Overview
The NCP1207ADR2, produced by onsemi, is a PWM Current-Mode Controller designed for free-running quasi-resonant operation. This controller combines a true current mode modulator and a demagnetization detector, ensuring full borderline/critical conduction mode in various load and line conditions. It features a dynamic self-supply (DSS) mechanism, eliminating the need for an auxiliary winding, and includes overvoltage protection (OVP) and overcurrent protection (OCP) for enhanced reliability.
Key Specifications
| Parameter | Min | Typ | Max | Unit |
|---|---|---|---|---|
| VCC Increasing Level at which the Current Source Turns-off | 10.8 | 12 | 12.9 | V |
| VCC Decreasing Level at which the Current Source Turns-on | 9.1 | 10 | 10.6 | V |
| Internal Soft-start Time | 1.0 | ms | ||
| Minimum TOFF (Internal Blanking Delay after TON) - NCP1207A | 8.0 | μs | ||
| Minimum TOFF (Internal Blanking Delay after TON) - NCP1207B | 4.5 | μs | ||
| Peak Current Source/Sink Capability | 500 | mA | ||
| Undervoltage Lockout for VCC Below | 10 | V | ||
| Internal Temperature Shutdown | 150 | °C |
Key Features
- Free-running borderline/critical mode quasi-resonant operation
- Current-mode with adjustable skip-cycle capability
- No auxiliary winding VCC operation due to Dynamic Self-Supply (DSS)
- Auto-recovery overcurrent protection
- Latching overvoltage protection
- External latch triggering, e.g., via overtemperature signal
- Internal 1.0 ms soft-start
- Internal temperature shutdown
- Direct optocoupler connection
- SPICE models available for transient analysis
- Pb-free and halide-free devices
Applications
The NCP1207ADR2 is particularly suited for applications where low part-count is crucial, such as in low-cost AC/DC adapters, consumer electronics, and auxiliary supplies. Its high-performance high-voltage technology makes it ideal for building rugged and reliable switch-mode power supplies (SMPS), including battery chargers where output voltage varies during operation.
Q & A
- What is the primary function of the NCP1207ADR2?
The NCP1207ADR2 is a PWM Current-Mode Controller designed for free-running quasi-resonant operation in switch-mode power supplies.
- What is the Dynamic Self-Supply (DSS) feature?
The DSS feature allows the controller to be directly connected to the high-voltage DC rail, eliminating the need for an auxiliary winding to supply the IC.
- How does the overvoltage protection (OVP) work?
The OVP works by sampling the plateau voltage after the turn-off sequence, and if an overvoltage condition is detected, the IC goes into a latched fault condition.
- What is the purpose of the demagnetization detection?
The demagnetization detection ensures borderline/critical conduction mode by triggering the turn-on event based on core reset detection.
- What is the significance of the internal timer in NCP1207A and NCP1207B?
The internal timer prevents the switching frequency from exceeding certain limits (8.0 μs for NCP1207A and 4.5 μs for NCP1207B) and avoids false leakage inductance tripping at turn-off.
- How does the skip cycle capability work?
The skip cycle capability allows the controller to enter burst mode when power demand falls below a predetermined level, preventing audible noise and reducing EMI.
- What is the role of the feedback section in the NCP1207ADR2?
The feedback section includes an internal pull-up resistor and a current setpoint division ratio, which are crucial for the controller's operation and feedback loop design.
- How does the NCP1207ADR2 handle overcurrent protection?
The NCP1207ADR2 features an overcurrent fault protection circuitry that continuously monitors the feedback signal, making the design rugged and reliable.
- What are the typical applications of the NCP1207ADR2?
Typical applications include low-cost AC/DC adapters, consumer electronics, auxiliary supplies, and battery chargers.
- Is the NCP1207ADR2 Pb-free and halide-free?
Yes, the NCP1207ADR2 is Pb-free and halide-free, making it environmentally friendly.
- How does the internal temperature shutdown work?
The internal temperature shutdown feature ensures that the IC shuts down at high temperatures (up to 150°C) to prevent damage and maintain reliability.
