KA3525A PWM Controller Symbol, Equivalents, Working Principle and Applications

Ⅰ. What is PWM controller?

Ⅱ. Overview of KA3525A PWM controller

Ⅲ. KA3525A symbol, footprint and pin configuration

Ⅳ. Technical parameters of KA3525A

Ⅴ. How does the KA3525A PWM controller work?

Ⅵ. What are the applications of KA3525A PWM controller?

Ⅶ. Absolute maximum ratings of KA3525A PWM controller

Ⅷ. How to measure the KA3525A good or bad?

PWM controller is an important part of power electronic equipment, mainly responsible for controlling and regulating the speed, power and torque of AC motor. This article describes in detail its basic concept, features, technical parameters, working principle and applications, so that you can better understand this controller.

Pulse width modulation refers to the control of analog circuits with the digital output of a microprocessor, which is a method of digitally encoding analog signal levels. Controlling analog circuits digitally can dramatically reduce the cost and power consumption of a system. Many microcontrollers contain PWM controllers within them. PWM has a very wide range of applications, such as power supplies, solar inverters, infinitely variable speed regulation of DC motors, and home UPS systems.

The KA3525A is a monolithic integrated circuit that includes all the control circuitry required for a pulse width modulation regulator. It is designed to drive N-channel power MOSFETs and is a current-controlled PWM chip. It contains internal components such as voltage reference, error amplifier, pulse width modulator, oscillator, undervoltage lockout, soft-start circuit, and output driver etc. The KA3525A is an improved version of the SG3524 with a switching frequency of up to 200kHz, which is suitable for driving N-channel MOS power tubes. In addition, the KA3525A utilizes a 16-pin DIP package process for easy mounting and layout in circuit boards.

Replacements and equivalents:

• MC34063A

• SG1525AJ

• TL494

• UC3525

The following picture shows the symbol, footprint and pin configuration of KA3525A.

Pin 1 (Inv. Input): This pin serves as the inverting input for the error amplifier. In a closed-loop system, it is linked to the feedback signal. However, in an open-loop system, this pin connects to the compensation signal input (pin 9) to create a follower configuration.

Pin 2 (Noninv. Input): It is the same direction input of the error amplifier. In closed-loop and open-loop systems, this terminal is connected to the given signal. Depending on the need, we connect different types of feedback networks between this terminal and the compensation signal input (Pin 9) to form proportional, proportional-integral and integral types of regulators.

Pin 3 (Sync): It is the external synchronization signal input of the oscillator. It can be synchronized with external circuits by connecting an external synchronization pulse signal to this terminal.

Pin 4 (OSC.Output): It is the oscillator output.

Pin 5 (CT): It is the oscillator timing capacitor input.

Pin 6 (RT): It is the oscillator timing resistor input.

Pin 7 (Discharge): It is the oscillator discharge terminal. An external discharge resistor is connected between this terminal and pin 5 to form a discharge circuit.

Pin 8 (Soft-Start): It is the access point of soft-start capacitor.

Pin 9 (Compensation): It is the PWM comparator compensation signal input. We connect different types of feedback networks between this terminal and pin 2, which can form proportional, proportional-integral and integral regulators.

Pin 10 (Shutdown'): It is the external shutdown signal input. When this terminal is connected to high level, the controller output will be disabled. This terminal can be connected to the protection circuit for fault protection.

Pin 11 (Output A): It is output A. Pin 11 and pin 14 are two complementary outputs.

Pin 12 (Ground): It is the signal ground.

Pin 13 (Vc ): It is the output stage bias voltage access.

Pin 14 (Output B): It is output B. Pin 14 and Pin 11 are two complementary outputs.

Pin 15 (Vcc): It is the bias power input.

Pin 16 (Vref): it is the reference power output.

The internal circuitry of the KA3525A consists of several links, including an error amplifier, comparator output transistor, oscillator, trigger and output logic control circuit.

First of all, the function of the error amplifier is to compare the input signal with the reference signal in order to realize precise control of the output voltage. The comparator is used to compare the output signal of the error amplifier with the triangular wave signal generated by the oscillator to produce the PWM control signal. The oscillator is responsible for generating the triangle wave signal and its discharge end is controlled by an external resistor to control the dead time. The soft-start terminal is controlled by an external soft-start capacitor, which is charged by a 50μA constant current source from the internal Uref.

The trigger generates corresponding trigger signals according to the phase relationship between the output signal of the comparator and the triangle wave signal generated by the oscillator. The output logic control circuit controls the on and off of the output triode according to these trigger signals to generate PWM control signals. Next, the output transistor will control the gate of the power switching tube according to these control signals, thus realizing the control of the microcontroller-based CNC switching power supply.

• Power management: KA3525A can be used for power management applications such as power switching control. It enables precise control of the power supply, extends the battery life of the device and improves the performance and stability of the device.

• Motor control: The KA3525A can also be used for motor control. It can control the speed and steering of the motor by adjusting the duty cycle of the PWM signal.

• LED lighting: It can step down the high voltage to a stable voltage suitable for LED operation and realize the brightness control of LED.

• Switching power supply controller: The KA3525A is often used in the design of switching power supplies that convert a DC voltage to a stabilized output voltage. It works by controlling the conduction and cutoff of the switching tubes to adjust the output voltage.

• Battery charger: We can use KA3525A to design a battery charger to control the charging current through PWM to ensure the safety and efficiency of the charging process.

To begin, the ohmmeter function of the multimeter is employed to inspect potential short circuits between the two output wires. If no short circuit is detected, a thorough examination of the wires or circuit board follows. Upon confirming the absence of a short circuit, the case is opened to assess the condition of the input fuse. Subsequently, a multimeter is utilized to identify breaks and opens in both input and output wires. In the presence of an open circuit, it becomes necessary to replace the corresponding input and output wires. Visual inspection and tactile examination are then performed to detect any loose or desoldered devices. If such issues are identified, they are promptly re-soldered.

If charging cannot be activated, please do not try to fix it by yourself, it is likely that the power chip driver circuit or other auxiliary circuits are damaged, resulting in the main chip not working. For this case, we need a professional repairer to use an oscilloscope to test it. Without an instrument, we can't detect it by ourselves, and even if we know which device is the problem, we can't replace it.

Frequently Asked Questions

1. What are the key features of the KA3525A?

Some key features include a wide input voltage range, adjustable dead-time control, an on-chip oscillator, and a high output current capability.

2. What is the function of KA3525A?

The KA3525A is a monolithic integrated circuit that Includes all of the control circuits necessary for a pulse width modulating regulator. There are a voltage reference, an error amplifier, a pulse width modulator, an oscillator, an under-voltage lockout, a soft start circuit, and the output driver in the chip.

3. What is the voltage of KA3525A?

This is a 16-pin chip with a reference output current of roughly 50mA and a supply voltage of around 40V. The operation temperature is 0 to 70 degrees Celsius, whereas the storage temperature is -65 to 150 degrees Celsius.

4. What is the typical application of the KA3525A?

The KA3525A is commonly used in switch-mode power supply (SMPS) designs, such as in DC-DC converters and AC-DC converters.