Abstract: Introduced pulse-duration modulation power amplifier SA51 and 16 monolithic integrated circuit MSP430F1121 basic characteristic, has given two piece of-like electrical machinery speed control system’s simple application method which and the electric circuit is composed of them.
Key word: SA51 MSP430F1121 pulse-duration modulation DCO capture
Present’s electronic installation often requests the volume to be small, the weight is light, the efficiency is high, usually under the harsh environmental condition, in the military product, the designer hoped especially the use monolithic or the biplate system by reduces the component quantity as far as possible. SA51 and MSP430F1121 become the composition biplate actuation control system’s ideal selection scheme by its own high integration rate and the formidable function. This plan may widely apply to the electrical machinery, in solenoid valve’s control system.
1 SA51 synopsis
1.1 SA51 characteristic parameters
SA51 is the pulse-duration modulation power amplifier which produces by American APEX Corporation, it can provide 5A for the load the uninterrupted current. This entire bridge amplifier can work in the very wide electric power supply scope, to the bridge upper arm and the forearm switch’s actuation and the control circuit mix integration in the component, the user only need provide with TTL the level compatible PWM signal may carry on four quadrant patterns the peak-to-peak value and the direction also controls, moreover and the digital controller’s connection is simple. The SA51 internal circuit may provide the suitable dead time gap to guarantee the apron four N trench field effect tube, the field effect tube’s breakover resistance is very low, but the shutter speed is very actually high (high may reach 500kHz), the efficiency may reach 97%. Regarding the idle/dormancy pattern or the error protection, SA51 provides has compatibly forbids the base pin with TTL to shut off four field effect tubes. SA51 uses 8 foot TO-3 seal, may install on the small radiator or welds directly installs on the print circuit wafer.
The SA51 electricity absolute rating is as follows:
* power line voltage Vs:80V;
* peak value output current: 7A;
* logic power line voltage Vcc:16V;
* internal power loss: 120W;
* base pin welding temperature (10s): 300℃;
* ambient temperature: 150℃;
* storing temperature: - 65~150℃;
* application temperature: - 65~125℃;
** input end input voltage: 0~Vcc;
* forbids the end input voltage: 0~Vcc.
1.2 SA51 structure functions
SA51 amplifier’s functional block diagram as shown in Figure 1. Is presently as follows various base pins’ functional description:
Vcc: Internal logic circuit and MOSFETS upper arm and forearm driver’s low pressure power source;
The Vs:H bridge electric power supply, MOSFETS obtains the output current from this power source end, this foot voltage range is the Vcc~ 80V, MOSFETS nominal value is 100V. This foot arrives at the place the shunt capacitor to be possible to filter the voltage to be passive, guaranteed that in the switch period power line voltage’s stability, this electric capacity should approach the Vs base pin as far as possible;
AOUT: Half bridge’s output foot A, when PWM input for high, this foot outputs is Vs;
BOUT: Half bridge’s output foot B, when PWM input for low, this foot outputs is Vs;
RSENSE: Two-and-a-half bridge forearm’s common junction, may connect one to examine the electric current to the Vs place examination resistance, in fact this foot may also link directly arrives at Vs the place. But this base pin is opposite in the Vs place biggest permission voltage ±2V;
GND: Input logic and Vcc place;
PWM input: Uses in inputting and TTL the compatible PWM signal, the dutyfactor between 0%~100%;
Import embargo: Uses in shutting off four MOSFETS tubes, this foot is when 1 is the shutdown, is when 0 enables.
2 MSP430F1121 synopses
2.1 MSP430F1121 major functions
MSP430F1121 is the monolithic integrated circuit which American TI Corporation produces, it uses the highly effective 16 RISC essence, has 27 instructions and the 125ns instruction cycles, uses 1.8~3.6V (high to 4.1V) the low voltage power supply, after the procedure code encryption, is unable to decipher. This monolithic integrated circuit only needs an external connection resistance and an electric capacity then realizes high accuracy slope A/D to transform, simultaneously may the serial online programming. This component has the formidable look-at-me function and reaches as high as 100,000 times scratches writes the number of times, its timer A in compares under the pattern to be possible to realize D/A to transform or the production pulse-duration modulation output signal conveniently. MSP430F1121 contains 4kB 256B Flash as well as 256B RAM, uses 20 foot SOWB or the TSSOP seal, P1, P2 port’s 14 I/O pin may program independently for the input, the output and the interruptible state, may also the whole take the port use.
2.2 MSP430F1121 clock systems
MSP430F1121 has ACLK (to be auxiliary clock), MCLK (main system clock) and SMCLK (subsystem clock) three kind of clocks. These three kind of clocks may by low frequency oscillator LFXT1CL after 1, 2, 4, 8 frequency divisions obtains the low frequency clock. MCLK and SMCLK may also by DCOCLK after 1, 2, 4, 8 frequency divisions obtains the high frequency clock. DCOCLK may the frequency which produces the DCO oscillator after software FLL obtains.
Figure 2 electrical machinery speed control schematic diagram
The DCOCLK software FLL method is: The DCO foundation frequency by the interior either the non-essential resistance the electric current which pours into to the DC generator decided that (may choose internal or piece external resistance by DCOR control position), when DCOCLK is 5MHz when the chip select internal resistance, DCOCLK is bigger than 5MHz, choice piece external resistance. Its foundation frequency may by resistance control position Rsel2, Rsel1, the Rsel0 frequency division 8 for the nominal frequency scope, then by control position DCO2, DCO1, DCO0 carry on the frequency division adjustment again, adjustment position MOD4~MOD0 may use in controlling DCO and between the DCO 1 two kind of frequency cuts.
Below is one establishes clock’s procedure, this procedure take the ACLK establishment as 4096Hz (LFXT1CLK/8=32768Hz/8=4096Hz), the DCOCLK establishment is 8MHz, MCLK and SMCLK chooses DCOCLK is the example carries on the compilation, delta=DCOCLK/ACLK=8M/4096=1953.
#include “msp430×11x1.h”
#include “stdio.h”
#define delta 1953
void setdco(void);
main(void)
{
WDTCTL=WDTPW WDTHOLD; // closes the watch-dog
BCSCTL1|=DIVA1 DIVA0; //ACLK =LFXT1CLK/8
BCSCTL2|=DCOR; // uses the non-essential resistance
Setdco();
}
void setdco(void)
{
int fir1, fir2, lable1=1;
fir2=0;
TACTL=TASSEL1 TACLR;
CCTL2=CCIS0 CM0 CAP;
TACTL|=MC1;
For (; lable1==1;)
{
lable2:
if((CCTL2&CCLFG)==0) // tests whether to catch the number
goto lable2;
CCTL2=CCTL2-CCLFG; // eliminates the capture symbol
fir1=CCR2;
fir1=fir1-fir2;
fir2=CCR2;
if(delta>fir1)
{DCOCTL=DCOCTL 1;
if (DCOCTL= =255)
{if((BCSCTL1&7) = =7)
lable1=0;
else
BCSCTL1=BCSCTL1 1;
}
}
if(delta<fir1)
{DCOCTL=DCOCTL-1;
if (DCOCTL= =0)
{if((BCSCTL1&7) = =0)
lable1=0;
else
BCSCTL1=BCSCTL1-1;
}
}
if (delta= =fir1)
lable1=0;
}
CCTL2=0;
TACTL=0;
}
2.3 ASP430F1121 establishments fixed time
Timer Timer-A has three capture/comparison module, compares under the pattern to be possible to produce the PWM signal conveniently. Below is a Timer-A capture/comparison module 1 in compares under the pattern to produce the dutyfactor is 50% PWM signal routine. Its PWM output pattern is the 3:PWM setting/replacement, changes CCR0 the value to be possible to change the PWM cycle (for example SMCLK=8MHz, then the P1.2 output PWM cycle is CCR0/8M=8000/8M=1ms), but changes CCR1 the value to be possible to change the dutyfactor (0%~100%).
#include “msp430×11x1.h”
#include “stdio.h”
main(void)
{
WDTCTL=WDTPW WDTHOLD; // closes the watch-dog
TACTL=TASSEL1 TACLR; // timer clock source chooses SMCLK
CCR0=8000;
CCTL1=OUTMOD0 OUTMOD1;
CCR1=4000;
P1DIR|=4;
P1SEK=|4;
TACTL|=MCO;
}
The timer Timer-A work in catches under the pattern to be possible to use in the time event’s pinpointing. If has selected pulse triggering on the designation input pin along, then the timer counting’s value will be duplicated in capture register CCRx. Below is the capture/comparison module 2 work in catches under the pattern routine, the timer clock source chooses SMCLK, increases the counting pattern, the capture source is the P1.3 foot input pulse, the capture number of times is 100 times, the capture frequency data puts in array READCCR2[].
#include “msp430×11x1.h”
#include “stdio.h”
main(void)
{int READCCR2[100];
WDTCTL=WDTPW WDTHOLD; // closes the watch-dog
TACTL=TASSEL1 TACLR; // timer clock source chooses SMCLK
CCTL2=CM0 CAP;
TACTL|=MCO;
for (I=0; I<100; I )
{TST:
IF((CCTL2&CCIF)==0)
GOTO TST;
CCTL2=CCTL2-CCIFG;
READCCR2[I]=CCR2;
}
}
3 electrical machinery speed control system’s design
Figure 2 is the low power electrical machinery speed control system schematic diagram which is composed of micro controller MSP430F1121 and driver SA51. In the chart, V1~V4 is the TVS tube (Transient Voltage Suggressor Diode: The transient voltage suppresses the diode), takes the responsibility a high energy instant when presses the pulse, its working impedance may immediately drop to the breakover value, allows the big electric current to pass, and the voltage clamp to the predetermined level, is exempt from by the effective protection circuit’s in precision primary device the damage. The clamp response time is only 1ps (10-12S), in the electric circuit uses the TVS tube to be possible to prevent Aout and the Bout output voltage effectively is higher than Vss or is lower.
Figure 2 U2 is the TPS77101 power source management chip, V0=Vref(1 R1/R2), Vref=1.1834V, chooses R2 is 30kΩ, if causes V0 is 4.0V, then R1 elected 72kΩ, to reduce the noise and suppress the vibration, when R1 and R2 should as far as possible the close SENSE end, on the electricity, RESET will provide to a monolithic integrated circuit reset signal.
Monolithic integrated circuit’s P2.0, P2.1 may take the electrical machinery four kind of modal control input end, the increase type encoder’s output pulse after the electro-optical isolation will send in catches I/O to carry P1.3, after will request condition and actual rotational speed comparison, after undergoing certain control algorithm processing, changes the CCR1 register’s value, thus the change modulation signal dutyfactor, passes through PWM to output I/O finally to carry P1.2 to output SA51 the PWM input end, controls electrical machinery’s rotational speed.
Here gives is only is composed of SA51 and MSP430F1121 drives the control the simple closed loop application, in fact, this kind of combination may apply in many situations, like transforms either the use serial communication using A/D carries on the simulation or the digital transformation and the position control and so on.
