65W notebook laptop power adapter circuit

The TOP269EG off-line switcher integrated circuit (IC), designated as U1, can be utilized in a flyback configuration to create a simple and highly efficient power adapter for notebook laptops. The TOP269EG features an integrated 725 V MOSFET and a multi-mode controller that regulates the output by modulating the MOSFET's duty cycle based on the current supplied to its CONTROL pin. Common-mode inductors L3 and L4 are employed to filter the AC input. A class X capacitor, C1, provides differential filtering, while resistors R1 and R2 ensure safety from electric shock in the event of AC removal by creating a discharge path for C1, which is a requirement from safety agencies for capacitors exceeding 100 nF. The bridge rectifier D1 converts the AC input to DC, and bulk capacitor C2 smooths the DC output. Capacitor C7 is responsible for the auto-restart timing of U1; it charges through the DRAIN (D) pin at startup, allowing U1 to commence switching once charged. Additionally, capacitor C7 aids U1 in utilizing an output overvoltage shutdown function. An increase in output voltage raises the bias winding on the primary side, which is monitored by VR1. When the bias voltage rises sufficiently, VR1 conducts and biases Q1 to inject current into the Voltage Monitor (V) pin of U1. If this current exceeds 336 µA, U1 enters overvoltage shutdown mode and latches off.

The circuit design employing the TOP269EG IC is characterized by its efficiency and simplicity, making it suitable for notebook laptop power adapters. The flyback topology allows for isolation between the input and output, enhancing safety and reliability. The integrated MOSFET reduces component count and simplifies the layout, which is advantageous for compact designs.

The common-mode inductors L3 and L4 are critical for minimizing electromagnetic interference (EMI), ensuring compliance with regulatory standards. The X class capacitor C1 plays a vital role in filtering high-frequency noise, while resistors R1 and R2 are essential for safety, providing a discharge path for C1 to prevent electric shock hazards. The bridge rectifier D1 is responsible for converting the AC voltage from the mains to a usable DC voltage, which is then smoothed by bulk capacitor C2, ensuring stable operation of the power supply.

Capacitor C7's function in the auto-restart feature is crucial for maintaining continuous operation. Upon initial power-up, C7 charges, allowing the IC to begin switching. In the event of an output overvoltage condition, the feedback mechanism involving VR1 and Q1 ensures that the system can safely shut down to prevent damage to the connected load. This feedback loop not only protects the power adapter but also enhances the overall reliability of the power supply system.

In summary, the design utilizing the TOP269EG IC in a flyback configuration provides a robust solution for power conversion in notebook laptops, combining safety features, efficient regulation, and compactness into a single integrated circuit solution.Using TOP269EG off-line switcher IC, (U1), in a flyback configuration can be designed a very simple high efficiency notebok laptop power adapter. TOP269EG IC has an integrated 725 V MOSFET and a multi-mode controller. It regulates the output by adjusting the MOSFET duty cycle, based on the current fed into its CONTROL pin.

Common-mode inductors L3

and L4 provide filtering on the AC input. X class capacitor C1 provides differential filtering, and resistors R1 and R2 provide safety from shock if the AC is removed, by ensuring a path for C1 to discharge. This is required by safety agencies when the capacitor value exceeds 100 nF. Bridge rectifier D1 rectifies the AC input, and bulk capacitor C2 filters the DC. Capacitor C7 provides the auto-restart timing for U1. At startup this capacitor is charged through the DRAIN (D) pin. Once it is charged U1 begins to switch. Capacitor C7 stores U1 utilizes an output overvoltage shutdown function. An increase in output voltage causes an increase in the bias winding on the primary side, sensed by VR1.

A sufficient rise in the bias voltage causes VR1 to conduct and bias Q1 to inject current into the Voltage Monitor (V) pin of U1. When the current exceeds 336 uA, U1 enters the overvoltage shutdown mode and latches off.

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