Overview
The L4981B, produced by STMicroelectronics, is a high-performance power factor corrector (PFC) pre-regulator integrated circuit. It is designed to achieve a very high power factor of up to 0.99, making it ideal for high-efficiency power supply applications. The L4981B is realized in BCD 60II technology and includes all the necessary control functions for designing a high-efficiency power supply with sinusoidal line current consumption. It can operate with mains voltages between 85V to 265V without any line switch.
Key Specifications
| Parameter | Min. | Typ. | Max. | Unit |
|---|---|---|---|---|
| Supply Voltage (VCC) | - | - | 19.5 | V |
| Operating Ambient Temperature | -40 | - | 125 | °C |
| Storage Temperature | -55 | - | 150 | °C |
| Power Dissipation at Tamb = 70°C (DIP20) | - | - | 1 | W |
| Power Dissipation at Tamb = 70°C (SO20) | - | - | 0.6 | W |
| Initial Oscillator Frequency Accuracy | 85 | 100 | 115 | KHz |
| Gate Driver Output Peak Current (Sink) | - | - | 2 | A |
| Gate Driver Output Peak Current (Source) | - | - | 1.5 | A |
| Turn On Threshold Voltage | 14.5 | 15.5 | 16.5 | V |
| Turn Off Threshold Voltage | 9 | 10 | 11 | V |
Key Features
- High Power Factor: Achieves a power factor of up to 0.99.
- Universal Input: Operates with mains voltages between 85V to 265V without any line switch.
- Average Current Mode PWM: Maintains sinusoidal line current consumption without slope compensation.
- Modulated Frequency Operation: The L4981B operates with modulated frequency, optimizing the size of the input filter.
- Integrated Protections: Includes overvoltage and overcurrent protections, with the overcurrent level programmable using external resistors.
- Soft Start and Under Voltage Lockout: Features soft start and programmable under voltage lockout with hysteresis.
- High Current Gate Driver: Bipolar and DMOS totem pole output stage can deliver peak current in excess of 1A.
- Load Feedforward: Allows modification of the multiplier output current proportionally to the load for faster response to load transients.
Applications
- High-Efficiency Power Supplies: Ideal for designing high-efficiency power supplies with sinusoidal line current consumption.
- Power Factor Correction (PFC): Used in PFC pre-regulator applications to improve power factor and reduce line current distortion.
- Industrial and Consumer Electronics: Suitable for various industrial and consumer electronic devices requiring high power efficiency and compliance with power factor regulations.
- LED Lighting and Power Adapters: Can be used in LED lighting systems and power adapters where high power factor and efficiency are critical.
Q & A
- What is the typical power factor achieved by the L4981B?
The L4981B can achieve a power factor of up to 0.99.
- What is the operating voltage range of the L4981B?
The L4981B operates with mains voltages between 85V to 265V.
- How does the L4981B handle frequency modulation?
The L4981B operates with modulated frequency, which can be adjusted using an external resistor connected to the rectified line voltage.
- What kind of protections are integrated into the L4981B?
The L4981B includes overvoltage and overcurrent protections, with the overcurrent level programmable using external resistors.
- How does the soft start feature work in the L4981B?
The L4981B features a soft start mechanism that gradually increases the output voltage to prevent inrush currents during startup.
- What is the purpose of the load feedforward feature in the L4981B?
The load feedforward feature allows the multiplier output current to be modified proportionally to the load, providing a faster response to load transients.
- What is the maximum gate driver output peak current of the L4981B?
The gate driver output can deliver a peak current in excess of 1A.
- How is the turn-on threshold voltage programmed in the L4981B?
The turn-on threshold voltage can be programmed using external resistors connected between specific pins and VCC or GND.
- What is the typical operating supply current of the L4981B after turn-on?
The typical operating supply current after turn-on is around 12 mA.
- What are some common applications of the L4981B?
The L4981B is commonly used in high-efficiency power supplies, PFC pre-regulators, industrial and consumer electronics, and LED lighting systems.
