| 摘要 |
A start circuit for a DC-DC switching converter power supply is disclosed and includes a relaxation oscillator connected to the DC voltage source for periodically generating a start pulse at a predetermined frequency. The start pulse is coupled to a power switch on the primary side of a power transformer and functions to cause the power switch to close for the duration of each start pulse. The secondary winding of the power transformer is coupled to an energy storage device such as a capacitor which stores the charge coupled across the power transformer each time a start pulse is generated. When sufficient energy has been stored in the capacitor in this manner, a circuit detects this energy level and causes the energy to be coupled to a pulse generator circuit also located on the secondary side of the power transformer. Sufficient energy as coupled to the pulse generator in this manner to enable the pulse generator to begin normal operation, the pulse generator thereupon outputs pulse width modulated pulses which are coupled across in isolator to the power switch to enable normal feedback control operation of the power supply.
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