Constant voltage switch power supply

Abstract

The invention discloses a constant voltage switch power supply. The power supply comprises a transformer (1), a main switch tube (Q1), a constant voltage controller (3), a power supply circuit (4), a feedback circuit (5), a current detection resistor (6) and a rectification filtering circuit (7). In the invention, the constant voltage controller is used to actively detect a work voltage provided by a power supply circuit in each switch period, and according to the size of the voltage, charging time of the power supply circuit is decided. When the work voltage provided by the power supply circuit is higher than a preset first reference voltage, the charging time is reduced. When the work voltage provided by the power supply circuit is lower than the preset first reference voltage, the charging time is increased. The work voltage provided by the power supply circuit does not change along with constant voltage switch power supply output power and complex design debugging of the power supply circuit is avoided. In addition, by using the constant voltage switch power supply, a requirement of constant voltage controller work voltage can be reduced; and a standard 5VCMOS technology can be used to manufacture the power supply and production cost is reduced.

Description

technical field [0001] The invention relates to the technical field of constant voltage switching power supply, in particular to a constant voltage switching power supply. Background technique [0002] figure 1 It is a circuit diagram of a typical constant voltage switching power supply in the prior art. figure 1 Among them, the power supply system of the constant voltage control chip 700 is composed of a resistor 640 , a capacitor 650 , a freewheeling diode 600 and an auxiliary winding NA of the transformer 100 . Its working principle is as follows: when the constant voltage switching power supply is just turned on, the capacitor 650 is charged through the resistor 640, and the constant voltage control chip 700 is in a shutdown state; When the voltage reaches a certain voltage, the constant voltage control chip 700 starts to work, turns on the power MOS 200, and the input winding NP of the transformer 100 starts charging. When the primary current in the input winding NP r...

AI Technical Summary

Problems solved by technology

However, since the transformer 100 is not in an ideal state, the voltage of the working voltage VCC not only changes with the change of the output voltage, but also increases with the increase of the output current, and decreases with the decrease of the output current.

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