IR1205S

DC-DC converters are often used in a wide variety of industries, ranging from automotive to industrial applications. The IR1205S is a DC-DC converter developed by International Rectifier, one of the leading manufacturers of integrated circuits (ICs) and power semiconductors for the switching power supply industry. This converter is a high-efficiency, low-profile, and cost-effective solution for applications requiring power conversion with tight space constraints.

The IR1205S is a flyback non-isolated regulator with a Dual-Mode Synchronous Rectifier (DMSR) controller. The controller is based on a fixed frequency constant off-time control with valley current-mode control correcting for valley voltage droop. The output voltage of the IR1205S can be programmed from 0.6V to 5.4V. Its maximum output current is 10A with an efficient peak efficiency of 88%.

To provide accurate and reliable output under varying conditions, the IR1205S also features self-protections: overvoltage protection (OVP) by comparing Vmon pin voltage with overvoltage threshold, undervoltage protection (UVP) by comparing current sense resistor voltage with an internal reference, and over-current protection (OCP). The OCP is done by sensing the voltage drop over the current sense resistor, and will protect the devices from being damaged due to excessive current load caught in an accidental shorting or overload. The IR1205S’s features also provide a soft-start, short-circuit protection, and temperature protection.

The working principle of the IR1205S is relatively simple and relies on the principle of transformer action. In its standby mode, the primary-side MOSFET acts as a bridge rectifier, receiving the input voltage and rectifying it. The peak voltage of this rectified wave is proportional to the input voltage. The primary-side MOSFET is then modulated by the control loop, producing a variable pulse width at a fixed frequency. This pulse will be transferred to the secondary-side, through the primary-side transformer, and then rectified to produce the output voltage.

The efficiency of the IR1205S largely depends on the drain-source on-resistance (RDS) of the MOSFETs. The on-resistance and power dissipation of the MOSFETs largely depend on their temperature, the input voltage, and the duty-cycle. By controlling the MOSFETs\' RDS, the IR1205S is able to achieve efficiency up to 88% and a low profile.

Theoretically, the power loss in a DC-DC converter can be calculated by considering the input voltage, the output voltage, the peak efficiency, and the load current level, using the formulae Power loss = ( (Input Voltage - Output Voltage) * Output Current) / Peak Efficiency. In practice, however, the AC mains voltage can experience significant fluctuations due to factors such as changes in generating plants, transmission lines, and load demand, which need to be taken into account for calculating the power loss.

The IR1205S is an extremely reliable DC-DC converter that operates in a wide range of input voltages and output levels. Its features, such as OVP, UVP, OCP, and thermal protection, allow it to protect itself in the event of an accidental overload or open circuit. By employing a patented synchronous rectification circuit, the IR1205S can achieve a high peak efficiency of up to 88 on various output currents. This makes the IR1205S a highly attractive option for applications requiring power conversion with tight space constraints.