说明

• DN06022/D, Reference design can be used at the front end of a power supply to ensure that the PWM controller has enough voltage to start correctly in low input voltage conditions. The design will maintain a 10V difference between Vin and Vout and is easily changed to provide other voltages. The PWM is CS5171. However, this circuit can be used with any boost controller or regulator. The current mirror circuit, comprising the dual PNP transistor Q1 and the associated resistors, establishes a current that depends on the voltage difference between Vin and Vout. The dual PNP transistor NST30010MXV6 has a Vceo of 30V so it is used in this example. If higher output voltages are required a device such as the BC856BDW1T1G has a Vceo of 65V