The SGAseries of pulse width modulator inte- grated circuits are designed to offer improved per- formance and lowered external parts count when used in designing all types of switching power sup- plies. A sync input to the oscillator al- lows multiple units to be slaved or a single unit to be synchronized to an external system clock. A single resistor betweenthe CT andthe dischargeterminals provide a wide range of dead time ad- justment. A shutdownterminal controls both the soft-start circu- ity and the output stages, providing instantaneous turn off through the PWM latch with pulsed shut- down, as well as soft-start recycle with longer shut- down commands. These functions are also control- led by an undervoltagelockout which keepsthe out- puts off and the soft-start capacitor discharged for sub-normal input voltages.
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SG Applications Control-Integrated circuit for SMPS SG Pulse frequency modulation and pulse width modulation are two types of techniques used in control integrated circuits for switch-mode power supplies.
In Pulse frequency modulation technique on time of pulse remains constant but the frequency increases with the increase in load. But the Pulse frequency modulation technique causes some issues in switch-mode power supplies. The width of the pulse or on time increase with the increase in load. Pulse width modulation also resolves the issues which occur in Pulse frequency modulation.
Therefore, Pulse width modulation is a preferred technique for control circuits of switch-mode power supplies. I will discuss these things in detail later in this article.
There are two types of PWM controller integrated circuits: current control PWM controller The voltage control method used a feedback voltage by comparing it with a reference value to set a duty cycle of PWM. In return to control the output voltage of SMPS.
While the current control method uses Output current from output inductor to compare it with the reference value and to set the duty cycle of PWM. I have used a voltage mode PWM controller in pure sine wave inverter. It provides two pulse width modulator signal which is a complement of each other. It is used to generate a PWM signal for power electronics projects and also for switch-mode power supplies.
It offers feedback circuitry to control the output voltage by comparing the feedback signal with a reference voltage. It has a protection circuitry that shutdown the PWM signal based on the feedback current limit. SG pinout diagram This is a pin configuration diagram and the functionality of each pin is provided in the next section. Features of SG It can operate with a supply voltage of between 8 and 35 volts.
It may damage above 40 volts. It also has an external oscillator synchronization pin. It has a pulse to pulse shutdown capability. The maximum power dissipation is about mW.
Other similar integrated circuits are SG, UC For further features and specifications check datasheet. It is used in maximum inverters available in the market. It is a 16 pin integrated circuit. It has two PWM outputs both are an inversion of each. If you want to know about the internal architecture of SG Search its datasheet.
Output pins can driver semiconductor devices up to a current range of 50mA. The description and functionality of each pin are given in the next section on the pinout of sg Working with the functionality of each pin The above diagram shows the pin configuration of SG Description of each pin is given below: Pin 1 is an inverting pin and pins 2 is a noninverting pin.
If the voltage on the inverting pin is greater than the voltage on the non-inverting pin, the duty cycle increases and if the voltage on the non-inverting pin is greater than the inverting pin, the duty cycle decreases. So you can use one pin for feedback through the voltage divider and one pin for the setting of a reference voltage. Pin 8 SS is used for soft starting for enabling output after some time. Greater the value of capacitance connected to pin 8, greater the soft-start time.
Pin 10 is shut down pin. Pins 11 and 14 are output pins. Pin 13 and 15 are power pins. Vc should be between volt and Vin should be between volt. Pin 16 is a reference pin and it is used to set reference voltage through pin 1 or 2. It can also be used to give 5 volts to shut down the pin in case you want to shut down sg through a push-button.
Example Circuit diagram SG Circuit diagrams of example below show the circuit diagram of sg which generates two inverted PWM signals. Users can adjust the width of PWM using a variable resistor shown in the feedback circuit. You can change the variable resistor value to adjust the resolution of PWM. In the above circuit diagram feedback from the output is used to get regulated voltage.
It is discussed in detail in Dc to dc converter using a push-pull topology part. Two Mosfets and ferrite core transformer are used in push-pull configuration mode.
This example circuit provides power regulated voltage output with the help of the feedback circuit. Variables resistor R10 provide voltage regulation feature. SG Applications It is used for power electronics applications like pure sine wave inverters. It is used to generate regulated voltage for dc to dc convert circuits like a buck converter, boost convert, cuk converter, and many others.
Other articles of pure sine wave inverter.
SG3525 Pulse width modulation controller IC
SG3525 Datasheet PDF - ON Semiconductor