A switch power supply and a soft start circuit thereof
A soft-start circuit, switching power supply technology, applied in the direction of electrical components, output power conversion devices, etc., can solve the problem that the power-on surge current and power-on surge voltage cannot be effectively reduced.
Inactive Publication Date: 2018-12-25
SHANGHAI LUMIXESS TECH
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Problems solved by technology
[0005] In view of this, the present invention provides a switching power supply and its soft-start circuit to solve the problem that the prior art cannot effectively reduce the start-up surge current and start-up surge voltage
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[0071] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.
[0072] The invention provides a soft start circuit of a switching power supply to solve the problem that the prior art cannot effectively reduce the start-up surge current and start-up surge voltage.
[0073] Specifically, the soft start circuit of the switching power supply, see Figure 5 , connected between the filter capacitor C of the switching power supply and the reference ground; the soft-start circuit of the switching power supply is as follows Figur...
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A switch power supply and a soft start circuit thereof are provided, The control unit outputs a control signal to the control terminal of the on-off switch, so that the on-off switch is kept in an offstate in an initial stage after the switching power supply is powered on, and the charging current of the filter capacitor is kept in a very small range due to the limitation of a first resistor anda second resistor with a large resistance value, and the charging voltage is slowly increased; and the on-off switch is controlled to turn on and off according to a preset rule in the regulation stage, so that the filter capacitor is intermittently charged under the preset voltage difference to ensure that the charging current is very small each time and the charging voltage shows a step rise oneby one cycle; Finally, after the voltage of the on-off switch on the filter capacitor satisfies the preset condition, the on-state is maintained after the on-state is turned on in the locking stage, so that the filter capacitor will not have large charge current and charge voltage step before the latter stage converter enters the normal working state; The boot surge current and the boot surge voltage of the switching power supply are effectively reduced.
Description
technical field [0001] The invention relates to the technical field of switching power supplies, in particular to a switching power supply and a soft start circuit thereof. Background technique [0002] Switching power supply, due to its high conversion efficiency and high power density, has been widely used in various power supply occasions. Since the power conversion components of the post-stage converter in the switching power supply work at high frequency, a filter capacitor C is usually set at the input end of the post-stage converter to filter out high-frequency noise and improve external electromagnetic interference; figure 1 Shown is a schematic diagram of the structure of a common switching power supply. [0003] see figure 1 , at the moment when the switch K0 is closed and the AC mains AC is connected, a charging current Ich will be generated to charge the filter capacitor C through the filter inductor L and the rectifier bridge; since the resistive impedance of ...
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Login to View More IPC IPC(8): H02M1/36
CPCH02M1/36
Inventor 陈忠
Owner SHANGHAI LUMIXESS TECH