三端可调节输出正电压稳压器之文献翻译

某大学毕业设计（文献翻译）

第17页

Since the LM317 is a floating regulator, it is only the voltage differential across the circuit which is important to performance, and operation at high voltages with respect to ground is possible.

Figure 17 Basic Circuit Configuration

Load Regulation

The LM317 is capable of providing extremely good load regulation, but a few precautions are needed to obtain maximum performance. For best performance, the programming resistor (R1) should be connected as close to the regulator as possible to minimize line drops which effectively appear in series with the reference, thereby degrading regulation. The ground end of R2 can be returned near the load ground to provide remote ground sensing and improve load regulation. External Capacitors

A 0.1μF disc or 1.0μF tantalum input bypass capacitor (Cin) is recommended to reduce the sensitivity to input line impedance.

The adjustment terminal may be bypassed to ground to improve ripple rejection. This capacitor (CAdj) prevents ripple from being amplified as the output voltage is increased. A 10 μF capacitor should improve ripple rejection about 15 dB at 120 Hz in a 10 V application. Although the LM317 is stable with no output capacitance, like any feedback circuit, certain values of external capacitance can cause excessive ringing. An output capacitance (CO) in the form of a 1.0μF tantalum or 25μF aluminum electrolytic capacitor on the output swamps this effect and insures stability.

某大学毕业设计（文献翻译）

Protection Diodes

第18页

When external capacitors are used with any IC regulator it is sometimes necessary to add protection diodes to prevent the capacitors from discharging through low current points into the regulator.

Figure 18 shows the LM317 with the recommended protection diodes for output voltages in excess of 25 V or high capacitance values (CO > 25 μF, CAdj > 10 μF). Diode D1 prevents CO from discharging thru the IC during an input short circuit. Diode D2 protects against capacitor CAdj discharging through the IC during an output short circuit. The combination of diodes D1 and D2 prevents CAdj from discharging through the IC during an input short circuit.

Figure 18 Voltage Regulator with Protection Diodes

Figure 19 D2PAK Thermal Resistance and Maximum Power Dissipation versus

P.C.B. Copper Length

某大学毕业设计（文献翻译）

第19页

Figure 20 ‘‘Laboratory’’ Power Supply with Adjustable Current Limit and Output Voltage

Figure 21 Adjustable Current Limiter Figure 22 5.0 V Electronic Shutdown Regulator

Figure 23 Slow Turn–On Regulator Figure 24 Current Regulator

From《1.5 A Adjustable Output,Positive Voltage Regulator》