Telecom Server AC/DC Supply: Dual Controller: Analog

Block diagram (SBD) Server AC/DC Power Supply and Telecom Rectifier using TI’s Analog PFC and PWM controllers, High performance drivers and transceivers.

 Design Considerations

The challenges faced by AC/DC power supply developers today are achieving high power factor, low THD, and high efficiency across line and load conditions, high power density or reduced size, high reliability, and low system cost. Advanced power topologies such as interleaved PFC, bridgeless PFC, phase-shifted full-bridge DC/DC, LLC resonant DC/DC, and ZVS PWM DC/DC are commonly employed in today's designs addressing these needs. Most AC/DC power supplies use dual PWM controllers, a PFC controller and a DC/DC controller.
TI's Continuous Conduction Mode PFC controller achieves CCM control with fewer circuit components reducing BOM cost. Interleaved PFC controllers cater well for higher power and higher density form factor applications. The interleaving offers both input and output ripple current cancellation allowing smaller EMI filter, boost inductor and bulk capacitor.
TI's PWM DC/DC controller portfolio includes controllers for the Flyback, LLC Resonant Bridge, Phase Shifted Full Bridge, and Active Clamp Forward Topologies commonly found in server AC/DC designs. The Flyback controller uses a frequency modulation scheme that optimizes efficiency across the output power range while also providing unmatched 125mW no load power consumption. The LLC resonant half bridge controller offers 'zero voltage switching' ZVS of the power MOSFETs, a bounded operating frequency range and minimal external components improving both efficiency and overall system cost. The Active clamp forward controller family offers improved efficiency over single switch forward converters by both reducing the stress and allowing a lower voltage main switch MOSFET and by using the active clamp to recycle the magnetizing energy of the main transformer. The Phase shifted full bridge controller remains to be the industry's controller of choice for higher power applications as it offers ZVS and other features that helps reduce stress of MOSFETs and increase efficiency.
The family of UCC27xxx MOSFET drives includes a complete range of single and dual low-side MOSFET drivers ranging from 2A to 9A sink and source. They are available in complimentary, inverted and non-inverted varieties.
TI's Integrated Hot Swap Power Controllers are optimized for nominal -48V systems. The devices provide load current slew rate control and peak magnitude limiting.
Most of the Hot Swap Controllers have digital interface for precise programming and monitoring and also have Power good and fault outputs.
Other high-performance analog parts are also available to provide critical system functions and features such as sensor feedback, isolation, communication transceivers. (Telecom Server AC/DC Supply: Dual Controller: Analog)

Telecom DC/DC Module. Analog

Block diagram (SBD) Telecom DC/DC Module using TI’s Analog Controllers, high performance drivers and transceivers.

Design Considerations

The challenges faced by Telecom DC/DC power supply developers today include achieving high efficiency, high integration (reduction in physical solution size), low system cost, ease of development. Power topologies such as active-clamp forward, half bridge, and full bridge are commonly employed in today’s designs to addressing these needs. A Telecom DC/DC power supply usually converts -48V to some intermediate voltage. Designs are typically comprised of a PWM controller geared toward a specific topology and MOSFET drivers. Certain PWM Controllers may integrate the MOSFET drivers.
The Telecom DC/DC market is usually dictated by brick size (full, half, quarter, eighth or sixteenth). The emergence of eighth and sixteenth bricks have resulted in new demand for the half-bridge converter, since the power levels in these packages are more in tune with those at which the half bridge topology excels. Along with reduction in physical size and an increase in power density, there is also an increasing number of features being added to the DC/DC converters that are required from a system level. These features include prebias startup, tracking, controlled startup and controlled shutdown capabilities. TI’s PWM controllers provide complete control functionality for each of the above requirements.
The center of the power supply is the controller, and it can be referenced to either the primary or secondary side ground. Both configurations can use a scheme where bias power for the controller is initially derived from a startup circuit; prior to a more efficient auxiliary winding of the transformer taking over once steady state operation is reached. A problem with the secondary side controller is that the bias power must come from the primary side (which has the wrong ground), upon power up. This problem can be overcome by using a separate isolated bias power converter to supply the current needed by the controller. This separate power supply can guarantee proper startup under all conditions.
Primary and Secondary side control each has advantages and disadvantages. In primary side control, the feedback signal must go from secondary side to primary side via isolation. This feedback will suffer from phase delay, which will hinder the control loop bandwidth and ultimately the response of the converter. Many converters use FETs for Synchronous Rectification and these require carefully managed gate drive. Hence, secondary side control has advantages in that it can directly drive these synchronous rectifiers, leading to improved response and higher performance over primary side control. Primary side control has advantages in that many designers are familiar with it, and that it is less complex.
Texas Instruments' portfolio of MOSFET drivers includes both primary side drivers as well as synchronous rectifier drivers. The UCC2720x family is recommended as a 120V primary side MOSFET driver. For applications that require greater efficiency and density, Synchronous Rectification is recommended to improve the efficiency of the power-subsystems' secondary-side circuitry. The TPS2822x driver family is recommended for Synchronous Rectification.
TI’s Integrated Hot Swap Power Controllers are optimized for nominal -48V systems. The devices provide load current slew rate control and peak magnitude limiting. Most of the Hot Swap Controllers have digital interface for precise programming and monitoring and also have Power good and fault outputs.
Other high-performance analog parts are also available to provide critical system functions and features such as sensor feedback, isolation, communication transceivers.(Telecom DC/DC Module. Analog circuits)

0V to 50 Volt Variable Regulator circuits.

this Regulator circuits is
very simple variable power supply circuit can be made using this electronic circuit diagram .This variable regulator circuit will provide an variable regulated output voltage , between 0 and 50 volts . The CA3140 operational amplifier compares the regulator output to a reference voltage , that depends on the R9 value.

The output voltage will be nominally twice the voltage between the positive input ( noninverting ) of the CA3140 and ground . The unregulated input voltage must be around 60 volts The output voltage can be set between 0 an 50 volts using R9 potentiometer .The 2N3055 transistors must be mounted on a heatsink , to prevent the overheating of transistors .

3-Wire Serial LCD Circuits using a Shift Register

74HC595 is a high-speed 8-bit serial in, serial or parallel-out shift register with a storage register and 3-state outputs.

The shift register and storage registers have separate clocks, SH_CP and ST_CP respectively. Data in the shift register is shifted on the positive-going transitions of SH_CP, and the content of shift register will be transferred to the storage register on a positive-going transition of the ST_CP. If we tie both the clocks together, the shift register will always be one clock ahead of the storage register. The 8-bit data of the storage register will appear at the parallel output (Q0-Q7) when the output enable (OE) is low.

In this project, SH_CP and ST_CP are tied together. So, if we want to receive a serially transferred 8-bit into parallel form at Q0-Q7, an extra clock pulse is required after transmitting the 8-th bit of serial data because the clocks are tied and the storage register is 1-clock behind the shift register. 

HD44780-based character LCD

 

 All HD44780 based character LCD displays are connected using 14 wires: 8 data lines (D0-D7), 3 control lines (RS, E, R/W), and three power lines (Vdd, Vss, Vee). Some LCDs may have LED backlight and so they may have additional connections (usually two: LED+ and LED-).

Providing detail explanation of individual LCD pin doesn't fall within the scope of this project. If you are a beginner with LCD, I recommend to read these two articles first from Everyday Practical Electronics magazine : How to use intelligent LCDs  

 The SH_CP (11) and ST_CP (12) clock inputs of 75HC595 are tied together, and will be driven by one microcontroller pin. Serial data from microcontroller is fed to the shift register through DS (14) pin. OE (13) pin is grounded and reset pin MR (10) is pulled high. Parallel outputs Q0-Q3 from 74HC595 are connected to D4-D7 pins of the LCD module. Similarly, Q4 output serves for RS control pin. If the LCD module comes with a built-in backlight LED, it can simply be turned ON or OFF through LED control pin shown above. Pulling the LED pin to logic high will turn the back light ON.

 Software 

A first, a bit of data fed to DS pin of 74HC595 appears at Q0 output after 2 clocks (because SH_CP and ST_CP are tied). So, sending 4-bit data (D4-D7) and an RS signal require 6 clock pulses till they appear at Q0-Q4 outputs respectively. When the LCD module is turned ON, it is initialized in 8-bit mode. A number of initializing commands should be sent to operate the LCD module in 4-bit mode. All the driver routines that are discussed here are written in mikroC compiler. They work only for a 16x2 LCD module. User can modify the initialization operations inside the Initialize_LCD() routine to account for other LCD configurations. The driver routines and their functions are described below. 

- Initialize_LCD() : It initializes the LCD module to operate into 4-bit mode, 2 lines display, 5x7 size character, display ON, and no cursor.

- Write_LCD_Data() : Sends a character byte to display at current cursor position. 

- Write_LCD_Cmd() : Write a command byte to the LCD module. 

- Write_LCD_Nibble() : Data or command byte is sent to the LCD module as two nibbles. So this function routine takes care for sending the nibble data to the LCD module.

- Write_LCD_Text() : This routine is for sending a character string to display at current cursor position.

- Position_LCD() : To change the current cursor position

At the beginning of your program, you need to define Data_Pin, Clk_Pin, and Enable_Pin to the chosen microcontroller ports. I am going to demonstrate here how to use these driver routines to display two blinking character strings, Message1 and Message2, at different locations. I am going to test our serial LCD module with PIC12F683 microcontroller. The test circuit is shown below.

Note: My PIC12F683 Settings

Running at 4 MHz internal clock, MCLR disabled, WDT OFF.

Clock, Data, and Enable lines are served through GP1, GP5, and GP2 ports.

/* 3-wire Serial LCD using 74HC595
Rajendra Bhatt, Sep 6, 2010
*/
 
sbit Data_Pin at GP5_bit;
sbit Clk_Pin at GP1_bit;
sbit Enable_Pin at GP2_bit;
 
// Always mention this definition statement
unsigned short Low_Nibble, High_Nibble, p, q,  Mask, N,t, RS, Flag, temp;
 
void Delay_50ms(){
 Delay_ms(50);
}
 
void Write_LCD_Nibble(unsigned short N){
 Enable_Pin = 0;
 // ****** Write RS *********
 Clk_Pin = 0;
 Data_Pin = RS;
 Clk_Pin = 1;
 Clk_Pin = 0;
 // ****** End RS Write
 
 // Shift in 4 bits
 Mask = 8;
  for (t=0; t<4; t++){
   Flag = N & Mask;
   if(Flag==0) Data_Pin = 0;
   else Data_Pin = 1;
   Clk_Pin = 1;
   Clk_Pin = 0;
   Mask = Mask >> 1;
  }
  // One more clock because SC and ST clks are tied
  Clk_Pin = 1;
  Clk_Pin = 0;
  Data_Pin = 0;
  Enable_Pin = 1;
  Enable_Pin = 0;
}
// ******* Write Nibble Ends
 
 void Write_LCD_Data(unsigned short D){
 RS = 1; // It is Data, not command
 Low_Nibble = D & 15;
 High_Nibble = D/16;
 Write_LCD_Nibble(High_Nibble);
 Write_LCD_Nibble(Low_Nibble);
 }
 
void Write_LCD_Cmd(unsigned short C){
 RS = 0; // It is command, not data
 Low_Nibble = C & 15;
 High_Nibble = C/16;
 Write_LCD_Nibble(High_Nibble);
 Write_LCD_Nibble(Low_Nibble);
}
 
void Initialize_LCD(){
 Delay_50ms();
 Write_LCD_Cmd(0x20); // Wake-Up Sequence
 Delay_50ms();
 Write_LCD_Cmd(0x20);
 Delay_50ms();
 Write_LCD_Cmd(0x20);
 Delay_50ms();
 Write_LCD_Cmd(0x28); // 4-bits, 2 lines, 5x7 font
 Delay_50ms();
 Write_LCD_Cmd(0x0C); // Display ON, No cursors
 Delay_50ms();
 Write_LCD_Cmd(0x06); // Entry mode- Auto-increment, No Display shifting
 Delay_50ms();
 Write_LCD_Cmd(0x01);
 Delay_50ms();
}
 
void Position_LCD(unsigned short x, unsigned short y){
 temp = 127 + y;
 if (x == 2) temp = temp + 64;
 Write_LCD_Cmd(temp);
}
 
void Write_LCD_Text(char *StrData){
 q = strlen(StrData);
 for (p = 0; p  temp = StrData[p];
  Write_LCD_Data(temp);
 }
 
}
 
char Message1[] = "3-Wire LCD";
char Message2[] = "using 74HC595";
 
void main() {
CMCON0 = 7;  // Disable Comparators
TRISIO = 0b00001000;  // All Outputs except GP3
ANSEL = 0x00; // No analog i/p
 
Initialize_LCD();
 
do {
 Position_LCD(1,4);
 Write_LCD_Text(Message1);
 Position_LCD(2,2);
 Write_LCD_Text(Message2);
 Delay_ms(1500);
 Write_LCD_Cmd(0x01);  // Clear LCD
 delay_ms(1000);
} while(1);
 
}