CN101762738A - Method for sampling average current of chopper in state of interrupted output current - Google Patents

Abstract

The invention discloses a method for sampling an average value of the output current of a chopper in the state of interrupted output current in the technical field of circuit control. The technical scheme of the method comprises the following steps of: obtaining basic parameters, such as switch frequency and the like, for the work of a switch tube of the chopper; sampling the input voltage and output voltage of the chopper under the condition of a given duty ratio D1 and sampling a current value Is at a midpoint of an output current rising interval; and calculating the average current value of the chopper in the state of the interrupted output current according to a certain algorithm after an input voltage value, an output voltage value and the current value at the midpoint of the output current rising interval of the chopper in the state of the interrupted output current. The method has the advantages of effectively improving the sampling accuracy of the average current of the chopper and greatly improving the working performance of the chopper.

Description

A kind of average current method of sampling of current of chopper in state of interrupted output

Technical field

The invention belongs to circuit control technology field, relate in particular to a kind of average current method of sampling of current of chopper in state of interrupted output.

Background technology

Under the continuous situation of output current, only need sample to the output average current sampling of chopper to the current value of output current first transition midpoint, just can obtain the mean value of output current easily.But when interrupted situation appears in output current because in a switch periods for some time electric current be zero situation, at this time just can not only obtain the mean value of output current by the current value of electric current first transition midpoint is sampled.

Summary of the invention

The objective of the invention is to, a kind of average current method of sampling of current of chopper in state of interrupted output is provided, be used to improve the average current sampling precision of chopper, thereby improve the serviceability of chopper.

Technical scheme of the present invention is, the average current method of sampling of the chopper under a kind of output current on-off state, and its embodiment comprises the following steps:

Step 1, at first to know the basic parameters such as switching frequency that the chopper switches plumber does;

Step 2, the chopper that needs to sample are at given dutycycle D ₁The time input and output voltage; And to the current value I of output current first transition midpoint _sSample;

Step 3, record after the current value of input voltage value, output voltage values and output current first transition midpoint at current of chopper in state of interrupted output, can pass through certain algorithm, calculate the average current value of chopper under the output current on-off state.

Effect of the present invention is that the sampling by to chopper input voltage, output voltage and output current first transition midpoint current value by certain algorithm, calculates the mean value of the chopper output current under the output current on-off state.This method can improve the employing precision of chopper average current effectively, improves the serviceability of chopper greatly.

Description of drawings

Fig. 1 is the circuit topology figure of the related chopper of the embodiment of the invention.

The output current wave figure of the chopper in state of interrupted that Fig. 2 provides for the embodiment of the invention

Embodiment

Below in conjunction with accompanying drawing, preferred embodiment is elaborated.Should be emphasized that following explanation only is exemplary, rather than in order to limit the scope of the invention and to use.The present invention describes as an example with buck chopper device circuit.Fig. 1 is the related buck chopper device circuit theory diagrams of the embodiment of the invention.As shown in Figure 1, chopper mainly comprises direct supply E, switching tube Q, energy storage inductor L, sustained diode etc.

Fig. 2 is the related output current wave figure when current of chopper in state of interrupted output of the embodiment of the invention.As shown in Figure 2, in the one-period T, the output current under the on-off state probably can be divided into D ₁, D ₂, D ₃Three intervals, wherein D ₁Be given dutycycle, at interval D ₁Last output current is in ascent stage; At interval D ₂Last output current is in the decline stage; At interval D ₃Last output current is zero.

The switching frequency of known chopper switches pipe is D in the dutycycle of given switching tube ₁The time, the input voltage of chopper is V _In, output voltage is V _oTo chopper output current wave first transition D ₁The current value of midpoint is sampled, and obtaining its midpoint current value is I _s

Yi Zhi electric current ascent stage slope of a curve in Fig. 2 is

$k_1=\frac{V_{\mathrm{in}}-V_o}{L}---\left(1\right)$

In the output current curve in Fig. 2, electric current last transition slope of a curve is

$k_2=-\frac{V_o}{L}---\left(2\right)$

So

$\frac{D_1}{D_2}=-\frac{k_1}{k_2}=\frac{V_{\mathrm{in}}-V_o}{V_o}---\left(3\right)$

{。##.##1},

$D_2=\frac{V_o}{V_{\mathrm{in}}-V_o}{D}_1---\left(4\right)$

If the output average current value of chopper is I _o, then can get

I _o＝I _s(D ₁+D ₂) (5)

To obtain in (4) formula substitution (5) formula

$I_o=I_s{D}_1(1+\frac{V_o}{V_{\mathrm{in}}-V_o})---\left(6\right)$

D in (6) formula ₁Given dutycycle, V _In, V _oAnd I _sCan be by the mean value of being that calculates at the current of chopper in state of interrupted output output current.

The present invention is applicable to the average current value sampling of current of chopper in state of interrupted output, can improve the sampling precision of average current value effectively, thereby improve the serviceability of chopper greatly.

The above; only for the preferable embodiment of the present invention, but protection scope of the present invention is not limited thereto, and anyly is familiar with those skilled in the art in the technical scope that the present invention discloses; the variation that can expect easily or replacement all should be encompassed within protection scope of the present invention.Therefore, protection scope of the present invention should be as the criterion with the protection domain of claim.

Claims (1)

1. the average current method of sampling of a current of chopper in state of interrupted output, its embodiment comprises the following steps:

Step 1: at first will know the basic parameters such as switching frequency that the chopper switches plumber does;

Step 2: need the sampling chopper at given dutycycle D ₁The time input voltage and output voltage; And to the current value I of output current first transition midpoint _sSample;

Step 3: record after the current value of input voltage value, output voltage values and output current first transition midpoint at current of chopper in state of interrupted output, by certain algorithm, can calculate the average current value of chopper under the output current on-off state.

Effect of the present invention is that the sampling by to chopper input voltage, output voltage and output current first transition midpoint current value by certain algorithm, calculates the mean value of the chopper output current under the output current on-off state.This method can improve the employing precision of chopper average current effectively, improves the serviceability of chopper greatly.

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