PMIC Circuit

 Deep Knowledge About PMIC Circuits Used in LCD TV Panels By Imran Ashraf 

Power Management Integrated Circuits (PMICs) are critical components in **LCD TV panels**, responsible for efficiently managing and distributing power to various subsystems such as the **T-Con board (Timing Controller), backlight LEDs, source/gate drivers, and audio/video processing chips**. Below is a detailed breakdown of their functions, architecture, and key considerations.

1. Role of PMIC in LCD TVs

PMICs in LCD TVs perform several essential functions:

Voltage Regulation: Converts input power (e.g., 12V/24V from SMPS) to required voltages (1.8V, 3.3V, 5V, ±15V, etc.).

Power Sequencing: Ensures correct startup/shutdown order to prevent latch-up or damage.

Backlight Driver Control: Manages LED backlight current (constant current drivers for mini-LED/OLED).

Efficiency Optimization  :Uses **buck, boost, and LDO regulators** to minimize power loss.

Protection Circuits: Overvoltage (OVP), overcurrent (OCP), and thermal shutdown (TSD).

2. Key PMIC Sub-Blocks in LCD TVs

A. DC-DC Converters (Buck/Boost)

Buck Converters  Step down voltage (e.g., 12V → 5V for T-Con).

-Boost Converters: Step up voltage (e.g., 12V → 24V for gate drivers).

- Synchronous vs. Non-Synchronous: Synchronous designs improve efficiency (>90%).

B. LED Backlight Drivers

Constant Current Drivers : For LED strings (PWM dimming control).

- Mini-LED Local Dimming  Requires multiple channels (up to 1000+ zones in high-end TVs).

- **OLED TV PMICs**: Use **high-voltage boost converters** (up to 60V for OLED panel bias).

### **C. LDOs (Low-Dropout Regulators)**

- Used for noise-sensitive circuits (e.g., T-Con logic, audio ICs).

- **Low noise & high PSRR** (Power Supply Rejection Ratio) for stable video signals.

### **D. Power Sequencing Controller**

- Ensures proper startup sequence (e.g., **T-Con before source drivers**).

- Prevents inrush current and voltage spikes.

### **E. Protection & Monitoring**

- **OVP/OCP/UVLO (Under-Voltage Lockout)**.

- **I²C/SPI Interface** for digital control and fault reporting.

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## **3. Advanced PMIC Features in Modern LCD TVs**

### **A. Dynamic Voltage Scaling (DVS)**

- Adjusts voltage based on load (saves power in dark scenes).

- Used in **high-refresh-rate (120Hz/144Hz) panels**.

### **B. Digital Power Management (Digital PMICs)**

- **Programmable via I²C/SPI** (e.g., adjusting backlight dimming curves).

- Supports firmware updates for adaptive power control.

### **C. Integration with T-Con & Source Drivers**

- Some PMICs integrate **gamma voltage buffers** for precise panel control.

- **eDP (Embedded DisplayPort) PMICs** manage power for high-resolution displays.

### **D. Thermal Management**

- **Smart heat dissipation** via load balancing.

- **Junction temp monitoring** to prevent overheating.

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## **4. Common PMIC ICs Used in LCD TVs**

| **Manufacturer** | **PMIC Model** | **Key Features** |

|-----------------|--------------|-----------------|

| **Texas Instruments** | TPS651xx | Dual-output (+15V/-15V) for T-Con |

| **Maxim Integrated** | MAX171xx | High-efficiency LED drivers |

| **ON Semiconductor** | FAN534x | Boost converter for OLED bias |

| **Richtek** | RT693x | Multi-channel backlight driver |

| **Dialog Semiconductor** | DA921x | Digital multi-phase buck converter |

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## **5. Design Challenges & Solutions**

### **A. EMI Issues**

- **Spread-spectrum clocking (SSC)** in DC-DC converters to reduce noise.

- **Shielding & proper PCB layout** (minimize high-frequency loops).

### **B. Power Efficiency**

- **Synchronous rectification** vs. diode-based designs.

- **Light-load efficiency modes** (PWM/PFM switching).

### **C. Mini-LED & Local Dimming Complexity**

- Requires **multi-channel PMICs** with precise current matching.

- **Hybrid dimming (PWM + analog)** for smooth brightness transitions.

### **D. Heat Dissipation**

- **Thermal vias & heatsinks** for high-current paths.

- **Dynamic power throttling** in high-temperature conditions.

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## **6. Future Trends in TV PMICs**

- **GaN (Gallium Nitride) PMICs** for higher efficiency and compact designs.

- **AI-based power optimization** (adjusts voltages based on content).

- **Fully integrated PMIC + T-Con SoCs** for slimmer designs.

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Conclusion

PMICs in LCD TVs are evolving with **higher integration, digital control, and advanced backlight management**. Understanding their architecture helps in troubleshooting power-related display issues (e.g., flickering, no backlight) and optimizing TV power consumption.