Application in the power of the electromagnetism stove is controlled of HT46R22 one-chip computer

Foreword

In recent years, with the gradual improvement of the environmental protection and awareness of saving energy, a kind of new developing green kitchen utensils –The electromagnetism stove is being popularized in the family. It has changed the traditional flame cooking way, utilizes the electromagnetic induction principle, make electric current through produce the magnetic field at the built-in coil, the magnetic force line in the magnetic field senses the ware made of iron, produce the little vortexes of countless high-speed sports, the enormous circulation energy produced in vortex is changed into effective heat energy, make pan have, heat while being at a high speed by oneself, heat the food directly finally. The thermal efficiency of the electromagnetism stove is more than 90%, it is ashless smokelessly at the same time, pollution-free, do not raise the room temperature, does not produce harmful substances such as the carbon monoxide,etc., safe environmental protection. The electromagnetism stove also adopts the microcomputer to control, can control the temperature at will. Just because of all above-mentioned advantages, the popularity of family of the electromagnetism stove in the developed country has already been more than 80%.

In order to improve electric conversion ratio, what the home electromagnetism stove is generally adopted is high-frequency electromagnetism stove, must electricity afford to commutate frequently worker, under high frequency, steady power output and measure, become difficult point and key point that design right away in real time. Adopting the Model A/D one-chip computer HT46R22 that Holtek Company produces can realize warm control definitely conveniently, measure in real time, call the police and measure and control with the power, this text introduces the realization that the power controlled emphatically.

A power controls the design principle

1.1 Operation principle of the electromagnetism stove

The operation principle of the electromagnetism stove, is formed by main circuit and control circuit. The intersection of 220V and alternating current add in in charge of harmonic changer of voltage that S makes up by the intersection of electric capacity and C1 and C2 and the intersection of inductor and L1 and IGBT after commutating and straining the wave in the main circuit. The changer mainly plays two pieces of function, first, change the worker into the high-frequency alternating current of 20- 40kHz frequently, second, can change the electric energy into the magnetism. The high-frequency alternating current is added on the excitation coil, through electromagnetic induction, act on the pan and have bottoms directly, produce the vortex, make the pan heat rapidly. The control circuit adopts the one-chip computer HT46R22 as mainly controlling the chip, it can realize a lot of essential detection and protection, produce PWM signal required to control from it at the same time, control the output power of the electromagnetism stove.

1.2 The power of the electromagnetism stove controls the principle

The power is controlled, it is under worker’s steady situation of alternating current frequently, the electromagnetism stove can be exported steadily according to the power presumed, in order to enable electromagnetism stove to work steadily. Because the electric current of load can reflect the size of output power, so, the target that controls can turn into the electric current of load, design the intersection of load and size of electric current to be by the intersection of PWM and signal at the same time empty than determine, empty and than large, load electric current loud.

That users set for the intersection of fire power and shelf ‘ Power shelf It is successively 1600W, 1400W, 1200W, 1000W, 800W, survey the output power W of the original electromagnetism stove , load electric current A , the electric voltage V of market , the load electric current measures the value CRU voltage V And PWM sky than relation set out in Table 1.

Table 1 output power and the intersection of load and electric current account for empty than wait for relation

Can get the intersection of PWM and signal, account for by Table 1 empty to take the intersection of relation and curve than and the load electric current.

Realization that power 2 controls

2.1 One-chip computer HT46R22

HT46R22 a high performance which Holtec Company produces simplifies the order and collects the one-chip computer, is especially suitable for the product design that the need A/D changed. It is in charge of the foot being distributed.

It has mouth of 3 I/Os, one PWM exports the passway. Functions such as his low consumption, programmable frequency division device, counter, oscillator choosing, many passway A/D changing, PC communication,etc., make it applied to industrial control, motor controlling, consumption products,etc. extensively.

2.2 The hardware is designed

What the control circuit is adopted is that pair closes the ring to control, the principle picture.

Foot 14 PD0 of the one-chip computer HT46R22 Can output one passway of PWM signals, it and electric current shoulder the feedback signal and control level to form the circuit and form direct current and control level through direct current, meanwhile, the electric current testing signal from main circuit and testing signal of the voltage form the sawtooth wave after the circuit happened in the sawtooth wave, sawtooth wave and direct current control level compare, get, control S of electromagnetism stove in the main circuit offer the control pulse shut off service.

Comparative voltage V invariable, and V- varies with output power, when output power is greater than to presume the power, get the control level of low level, output narrowly and open the pulse, reduce output power, vice versa. In this way, close the ring and regulate and control achieving the goal of stabilizing output power through one.

2.3 Software design

The software design that the power controls is a main part of the software design of an electromagnetism stove, adopt the programming of assembler language, among them the variable explains as follows:

1It indicates heatflg 1 is in order to heat, 0 is in order to fix warmly, starting the machine turns 1 initially to heat / fix the warm state and switch over, only the keyboard can change this sign;

2It is effective to heat shelf location register heatreg and counter heatcnt heatreg 5 high low level, every one heats the shelf correspondingly, it is more convenient for heatreg7 to control revealing in order to keep warm; Heatcnt go on, count to 5 shelf, 0, for fry, control, consult table to be relatively more convenient; Starting the machine initially heatreg =f7h, heatcnt =0,In order to fry the shelf, only the keyboard can change this sign;

3Minimum control of fire changes the regular counter minpowcnt after the timer reduce it to 0 when cut off, spread into main program, eep Shi warm as in, heat, the main program resets this counter, and will control the line to overturn.

Source program and explanation are as follows:

; The power is controlled

powctrl:

mov r0, a ; In order to calculate PWM as follows =128* Ptab/VOL- 28

mov a, 80h

mov r1, a

call mul ; ro,r1 =128* Ptab

mov a, VOLADN

add a, offset adcbfr

mov mp, a ; Point to the city electric voltage ADC value

mov a, j ar

mov r2, a

call div ; r1 =r0,r1/VOL

mov a, r1

sub a, 28 ; PWM =R1- 28, the value is in A

mov r0, a

sub a, 127

snz cy ; Does not PWM exceed upper limit

jmp powctrl1 ; Whether not

mov a, 126

jmp powctrl3

powctrl1:

mov a, r0

sub a, 38

sz cy ; Does not PWM exceed lower limit

jmp powctrl2 ; Whether not

mov a, 38 ; Yes

jmp powctrl3

powctrl2:

mov a, r0

powctrl3:

r1 acc

mov pwm, a

; Control the line to control

snz heatflg ; Do not heat the state

jmp keephdl ; Deny, change over to definitely warmly and control

snz heatreg.7 ; Yes, the shelf negation of keeping warm

jmp chgctrl ; Yes

clr control ; Deny, open and control the line

jmp endputhdl

chgctrl:

sz minpowcnt ; Yes, do not get for 3 seconds

jmp chgctrl1 ; Whether not

mov a, MINPTIME* 4 ; Yes

mov minpowcnt a ; Reset the lowest fire power counter

sz control ; Is it effective to control the line to export at present

jmp chgctrl2 ; Whether not

set control ; Yes, put and control the line effectively

mov a, 50

mov ctrlcnt, a

jmp chgctrl1

chgctrl2:

clr control ; Can control the line to make effectively

chgctrl1:

jmp endputhdl

3 concludes the speech

Adopt the above-mentioned power control method to control the power output of the electromagnetism stove, its floating range of power can be controlled within 50W effectively. Prove, the performance of the electromagnetism stove is steady, so, the above-mentioned power control method is feasible through the real products, it is a method that is worth popularizing.

The source of this text: Technical application of power