DC power supply small automatic switching power supply
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DC power supply small automatic switching power supply
The switching power supply can be automatically charged, and at the same time has the compensation function of the negative temperature characteristic of the DC power supply. The working principle is as follows: when the source is charged, because the terminal voltage is low, the voltage across the capacitor C is also low, which is not enough to trigger the SCR2 to be turned on, and the SCR2 is turned off. At this time, the current is controlled by D1→R1→R4→D2→SCR:, so that the SCR: is turned on and the power is charged. As the charging process continues, the terminal voltage gradually increases, and the voltage across the capacitor C also increases. When the charging voltage reaches a predetermined value, the C-terminal voltage also reaches the trigger voltage of SCR2, and SCR2 is turned from the off state to the on state, then the control pole current of SCR1 is zero, SCR1 is turned off, and charging is stopped.
AC steady current switching power supply for DC power supply
The principle of the AC steady current switching power supply is relatively simple, and the step-down rectification part is omitted. A self-excited multivibrator is constructed by using a 555 time base circuit, and two power transistors of BG1 and BG2 are power outputs thereof. D1, D2 and filter capacitors C2 and C3 form a voltage doubler rectifier circuit, and the output is sent to the input end of the three-terminal voltage regulator integrator 7805. The AC steady current power source composed of 7805, R5, and D3 generates a constant charging current pair. The power is charged. If the component is selected as shown in the figure, the charging current of the circuit is 50mA, which is usually charged for 14 hours.