Overview
The NCP1207AP, 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 to ensure full borderline/critical conduction mode in various load and line conditions. It features high-voltage technology, allowing direct connection to the high-voltage DC rail, and incorporates several key features to build rugged and reliable switch-mode power supplies (SMPS).
Key Specifications
| Parameter | Description | NCP1207A | NCP1207B |
|---|---|---|---|
| Internal Timer Duration | Minimum TOFF | 8.0 μs | 4.5 μs |
| Maximum Switching Frequency | Below 125 kHz | Up to 200 kHz | |
| Peak Current Source/Sink Capability | 500 mA | 500 mA | |
| Undervoltage Lockout (VCC) | Below 10 V | Below 10 V | |
| Internal Soft-Start | 1.0 ms | 1.0 ms | |
| Overvoltage Protection (OVP) Reference Level | 5.0 V (adjustable) | 5.0 V (adjustable) | |
| Package Options | PDIP-8, SOIC-8 | PDIP-8, SOIC-8 |
Key Features
- Free-Running Borderline/Critical Mode Quasi-Resonant Operation
- Current-Mode with Adjustable Skip-Cycle Capability
- No Auxiliary Winding VCC Operation (Dynamic Self-Supply)
- Auto-Recovery Overcurrent Protection
- Latching Overvoltage Protection
- External Latch Triggering (e.g., via Overtemperature Signal)
- Internal Temperature Shutdown
- Direct Optocoupler Connection
- SPICE Models Available for Transient Analysis
- Pb-Free and Halide-Free Devices
Applications
The NCP1207AP is particularly suited for applications where low part-count and high reliability are crucial. Typical applications include:
- Low-cost AC/DC adapters
- Consumer electronics
- Auxiliary power supplies
- Battery chargers with variable output voltage
Q & A
- What is the primary function of the NCP1207AP?
The NCP1207AP is a PWM Current-Mode Controller designed for free-running quasi-resonant operation in switch-mode power supplies.
- What are the key benefits of the Dynamic Self-Supply (DSS) feature?
The DSS feature simplifies transformer design by eliminating the need for an auxiliary winding, providing a fully independent VCC level, and is particularly useful in applications with variable output voltage.
- How does the Overvoltage Protection (OVP) work?
The OVP detects overvoltage conditions by sampling the plateau voltage on the demagnetization winding and enters a latched fault condition if an overvoltage is detected, requiring a VCC cycle down to 4 V to reset.
- What is the purpose of the adjustable skip cycle level?
The adjustable skip cycle level allows the designer to tailor the level at which the skip cycle takes place, ensuring noise-free operation and fixing the maximum switching frequency in light load conditions.
- How does the Overcurrent Protection (OCP) function?
The OCP continuously monitors the FB line activity and enters burst mode during an overload, preventing thermal runaway and resuming operation once the fault condition disappears.
- What are the package options available for the NCP1207AP?
The NCP1207AP is available in PDIP-8 and SOIC-8 packages.
- What is the significance of the internal soft-start feature?
The internal soft-start feature, which lasts 1.0 ms, helps in gradually increasing the output voltage during startup, preventing high inrush currents.
- How does the demagnetization detection work?
The demagnetization detection is done through an auxiliary winding, which also enables fast Overvoltage Protection (OVP) and ensures the converter operates in the minimum of the drain-source wave.
- What is the maximum peak current source/sink capability of the NCP1207AP?
The NCP1207AP has a peak current source/sink capability of 500 mA.
- Is the NCP1207AP Pb-Free and Halide-Free?
Yes, the NCP1207AP is Pb-Free and Halide-Free.
