STR4A164HD

STR4A164HD Application Field and Working Principle

STR4A164HD is a type of PMIC (Power Management IC) from Rectron, a digital IC provider that manufactures AC DC converters and offline switching converters.

The STR4A164HD is an integrated AC DC converter based on a switching power regulator, with a low stand-by current, adjustable output voltage and low THD (Total Harmonic Distortion). It is suitable for many applications, such as lighting, appliance and consumer electronics, with an output current up to 30A.

The features of STR4A164HD include integrated auto-restart, overload protection, short-circuit protection and overvoltage protection. It is also equipped with soft-start feature and adjustable oscillator frequency, making it suitable for lowripple applications.

The working principle of STR4A164HD is based on a basic switching regulator circuit. It is composed of an input capacitor C1, an output capacitor C2, transformers T1 and T2, a switch S, an inductor L, a diode D1 and D2, a control IC U1, an oscillator U2, a voltage detector U3, a softstart capacitor C3, and a bias resistor R1.

The input AC voltage is rectified by the bridge rectifier circuit, producing a constant DC voltage which is then used to be applied to the input terminals of the STR4A164HD power converter module. The integrated control IC then uses the input DC voltage to constant the output voltage, by controlling the switching on and off actions of the switch S. The magnitude of the output voltage is adjustable by adjusting the bias resistor R1.

When the switch S is on, energy is transferred from the input side to the main transformer T1, inducing a voltage in the secondary coil of T1. The voltage is rectified by diode D1 to generate a DC voltage, which then charges the output capacitor C2 and produces the desired output voltage. When the switch S is off, the stored energy of the inductor L is transferred to the output side and the output voltage is maintained by the flyback action. At the same time, the current from the secondary coil of T2 is inverted by diode D2 and then stored in the input capacitor C1, which maintains the DC voltage supplied to the controller IC.

The STR4A164HD is also equipped with an oscillator U2 for setting up the frequency of the switching. This is necessary to reduce the value of switching losses, to increase the system efficiency and to reduce EMI noise. The adjustable soft start circuit of U3 controls the duration of the soft-start of the converter, so that it starts smoothly and stably with no overcurrent.