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Secondary time-delay soft start circuit of DC/DC convertor

A technology of soft start circuit and delay circuit, which is applied in the direction of electrical components, output power conversion devices, etc., and can solve problems such as failure to start normally, DC/DC converter output voltage overshoot, etc.

Inactive Publication Date: 2008-10-01
ASTEC POWER SUPPLY (SHENZHEN) CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

If the soft-start capacitor cannot be fully discharged during this period, it will cause the output voltage to overshoot when the DC / DC converter is restarted, or even fail to start normally.
However, in order to satisfy the requirement that the soft-start capacitor can be fully discharged when the input voltage drops, the capacity of the soft-start capacitor should not be large, otherwise, the output voltage rise time of the DC / DC converter will be relatively short, which cannot meet the user's requirements, that is, the input voltage drops There is a contradiction between the timely discharge of the soft start capacitor and the rise time of the output voltage

Method used

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  • Secondary time-delay soft start circuit of DC/DC convertor
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  • Secondary time-delay soft start circuit of DC/DC convertor

Examples

Experimental program
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specific Embodiment approach 1

[0020] Such as figure 1 The shown DC / DC converter secondary delay soft-start circuit includes a soft-start capacitor C1 connected in parallel between the non-inverting input terminal B of the error amplifier and the common ground. There is a controllable switching device Q1 whose output terminal is connected in parallel with the soft-start capacitor C1. The controllable switching device Q1 is a MOSFET, and its controllable input terminal is connected to a Г-shaped resistor composed of a delay resistor R3 and a delay capacitor C2. The output end of the capacitance delay circuit is connected, and the input end of the resistance capacitance delay circuit is connected with an input end A of a matched indication signal source belonging to the primary side of the DC / DC converter. The two ends of the delay resistor R3 are connected in parallel with a discharge diode D1 to quickly discharge the voltage of the delay capacitor C2. There is also a voltage stabilizing device Z1 that prov...

specific Embodiment approach 2

[0024] Such as figure 2 The shown DC / DC converter secondary delay soft-start circuit is different from the circuit in the first embodiment in that the controllable switching device Q1 is changed from a MOSFET to an NPN switching transistor, and the gate of the NPN switching transistor and the resistor A coupling resistor R4 is added between the output terminals of the time-delay circuit. The function of the delayed soft start is the same as that of the specific embodiment 1, and the soft start process is also basically the same.

specific Embodiment approach 3

[0025] Such as image 3 The difference between the shown DC / DC converter secondary delay soft-start circuit and the circuit of Embodiment 1 is that the bleeder diode D1 connected in parallel with the resistor R3 of the RC delay circuit is omitted. Since the function of the bleeder diode D1 is to accelerate the discharge of the capacitor C2 when the DC / DC converter is turned off, properly selecting the parameters of the capacitor C2 and the resistor R3 and omitting the bleeder diode D1 will not affect the delayed soft-start function of the circuit. The soft start process is also basically the same as that in the first embodiment.

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Abstract

A DC / DC convertor secondary time-delay soft start circuit comprises a soft start capacitor which is in parallel connected between the in-phase input end of the error amplifier and the common earth. The soft start circuit is provided with a controllable switching element which is in parallel connected with a soft starting capacitor at the output end. The controllable input end of the controllable switching element is connected with the output end of the capacitance-resistance time delay circuit. The input end of the capacitance-resistance time delay circuit is connected with the input end of an auxiliary indication signal source which belongs to the original edge of DC / DC convertor. The time-delay soft start circuit according to the invention can effectively settle the contradiction between the in-time electric discharge and the ascending time of the output voltage when the input voltage descends. When the DC / DC convertor is opened, the indication signal from the original edge is used for controlling the discharging of the secondary soft start capacitor. The fast re-electrifying when the input voltage descends is settled. The soft start problem of DC / DC convertor is realized. And the primary soft start and secondary soft start can be better assorted with each other through regulating the action time of the secondary soft start by the capacitance-resistance time delay circuit.

Description

technical field [0001] The invention relates to a starting circuit, in particular to a DC / DC converter secondary delay soft start circuit. Background technique [0002] The DC / DC converters used in communication power supplies are generally equipped with soft-start circuits to avoid large start-up overshoot currents and start-up oscillations. The soft start of the isolated DC / DC converter usually includes the soft start of the primary side and the soft start of the secondary side. Since the soft start of the primary side will overshoot and drop when the DC / DC converter is turned into normal operation after the startup is completed, a soft start circuit is also provided on the secondary side. In traditional soft-start circuits, soft-start capacitors are generally connected in parallel at the reference terminal, or are connected in parallel with the soft-start capacitors through the output terminal of the error amplifier. But no matter where the soft-start capacitor is conne...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02M1/36
Inventor 张式春施三保程杰斌
Owner ASTEC POWER SUPPLY (SHENZHEN) CO LTD