Design of Multi-channel AC/DC Output Power Supply Using KA1M0880 and CW4960

“This circuit contains high voltage MOS field effect transistor and perfect internal protection circuit, including: soft start circuit, internal oscillator circuit, feedback control circuit, overload protection circuit and thermal shutdown circuit, etc. KAIM0880 adopts TO-3P5 pin package, which is very convenient to use. At the same time, it can save the trouble of pairing and screening of additional power switch management.

“

1 Overview

2 Internal functions

Design of Multi-channel AC/DC Output Power Supply Using KA1M0880 and CW4960

KAIM0880 is a high-efficiency, high-stability, high-voltage PWM series circuit with less peripheral components produced by Samsung. Its functional block diagram is shown in Figure 1.

This circuit contains high voltage MOS field effect transistor and perfect internal protection circuit, including: soft start circuit, internal oscillator circuit, feedback control circuit, overload protection circuit and thermal shutdown circuit, etc. KAIM0880 adopts TO-3P5 pin package, which is very convenient to use. At the same time, it can save the trouble of pairing and screening of additional power switch management.

3 Circuit characteristics and electrical parameters

The characteristics of the KA1M0880 circuit are as follows:

● Contains high voltage, high current MOS field effect transistor;

●With overheating protection circuit;

●With output overcurrent protection circuit;

●With a wide voltage range of 85 ~ 265V (AC);

●With reliable soft-start function;

●Internal oscillation frequency can be selected from 50kHz, 70kHz, 100kHz;

●Only few peripheral components;

●Efficient gate drive to reduce switching losses.

The main electrical parameters of KA1M0880 are listed in Table 1.

4 Design examples

With the KA1M0880, it is very convenient to design a multi-channel AC/DC output power supply that is widely used in communication equipment. Figure 2 shows a complete multi-channel output AC/DC circuit. The output effective power of this AC/DC circuit can reach 94W. The output of the high-voltage switching transformer in the figure has only one winding, which can make the sampling voltage very stable. If the multi-channel voltage is directly output through the multi-winding, the sampling voltage will be extremely unstable due to the fluctuation of various loads and the mutual influence between the various channels, and even lead to the entire power supply at high temperature, low temperature, high input or It does not work properly at low input voltages. In addition, the interference noise voltage caused by this is also very large, so the sampling voltage in Figure 2 is sent to the precise adjustment circuit after being rectified by high frequency, and sent to the control terminal of the KA1M0880 through photoelectric coupling, so that the entire The control loop is stable. Three CW4960 synchronization circuits are provided in parallel by the external circuit, which can make the output interference noise smaller. And if it is converted by MAX629 and then sent out a negative power supply of -5V/200mA, it can be adapted to various applications. The design method of the switching transformer in the circuit is shown in Figure 3.

Table 1KA1M0880 electrical parameters