High-voltage starting circuit with constant current control

Abstract

The invention discloses a high-voltage starting circuit with constant current control, which is applied to a switch power supply. The high-voltage starting circuit comprises a high-voltage junction transistor, a control transistor, a current detecting resistor and a bias resistor, wherein a drain pole of the high-voltage junction transistor is coupled with a high-voltage power supply, a grid poleis coupled to the drain pole of the control transistor, and a source pole is coupled to the current detecting resistor; the current detecting resistor supplies the negative bias of the grid-source pole of the high-voltage junction transistor by constant voltage drop generated in a such a way that the current of the high-voltage junction transistor flows across both ends of the detecting resistor and enables the high-voltage junction transistor to output constant current; one end of the bias resistor is coupled to the grid pole of the high-voltage junction transistor, and the other end is coupled to the output end of the high-voltage starting circuit so that the grid pole voltage of the high-voltage junction transistor is equal to output voltage and the grid-source pole of the high-voltagetransistor maintains the constant negative bias so as to supply the constant output current.

Description

technical field [0001] The invention relates to a high-voltage starting circuit with constant current control, which is applied to a switching power supply, and can be used for a high-voltage power supply with a wide input range to generate a constant current output, so that the output current and time of the starting circuit are fixed, and it can prevent short circuit at the output end. The output current caused by abnormality is too large and the components are damaged. Background technique [0002] see figure 1 , which is one of the existing high-voltage starting circuits. Such as figure 1 As shown, this existing high-voltage start-up circuit uses a high-voltage junction transistor gate-source negative bias to limit the output current, and includes a high-voltage junction transistor Q1, a first metal-oxide-semiconductor field-effect transistor Q2, and a second MOSFET Q3, a bias resistor R1, a PNP transistor Q4, a Zener diode ZD1, and a hysteresis comparator COMP1. The...

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Problems solved by technology

[0007] As the output voltage rises with time, the gate-source voltage Vgs(Q1) of the junction transistor changes, so the output current will gradually decrease. In order to provide sufficient output current, the current limit point of the output current at the moment of startup must be increased. When a short circuit occurs at the output terminal It is easy to cause excessive power consumption and burn out

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