A voltage stabilizing circuit with hold time function

Abstract

A voltage stabilizing circuit with a holding time function, including a three-terminal integrated voltage regulator, an input filter capacitor and a rectifying diode. There is a holding time circuit connected in parallel between the input or output end of the three-terminal integrated voltage regulator and the common ground. The holding time circuit is composed of a charging resistor and a discharging diode connected in parallel and then connected in series with a charging and discharging capacitor for holding time. Two-terminal network, one end of which is the cathode of the discharge diode is connected to the input or output of the three-terminal integrated voltage regulator, the anode of the discharge diode is connected to the positive pole of the charging and discharging capacitor for the holding time, and the other end is the negative pole of the charging and discharging capacitor for the holding time. common connection. Realized the separation of the normal filter capacitor for the voltage stabilizing circuit and the charging and discharging capacitor for the holding time, and the charging and discharging capacitor for the holding time is an arbitrary capacity capacitor to ensure that the output voltage of the voltage stabilizing circuit meets the required holding time, effectively avoiding the power module due to selection The problem of difficult startup caused by large-capacity retention time capacitors.

Description

technical field [0001] The invention relates to a voltage stabilizing circuit, in particular to a voltage stabilizing circuit with the function of maintaining time. Background technique [0002] Such as figure 1 The post-stage voltage stabilization circuit of the three-terminal fixed integrated voltage regulator shown is widely used in power supplies. In order to keep the output voltage for a certain period of time, the capacity of the filter capacitor C1 is required to be large enough, and the large-capacity capacitor is used when the power supply starts. When it is equivalent to a short circuit, the larger the capacity of the filter capacitor C1, the higher the current peak value of the rectifier diode D1 charging it and the longer the time. After the charging current is converted to the primary side through the transformer, a higher peak current will be generated, which makes the peak current protection design a difficult problem. On the one hand, the peak protection is...

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Problems solved by technology

On the one hand, the peak protection is required to be sensitive, but it will cause the charging current of the filter capacitor C1 to be too large during startup and trigger the peak current protection circuit to malfunction, causing the power module to fail to start smoothly, which generally manifests as "hiccups". For this situation, the peak protection action threshold is It should be increased appropriately; on the other hand, the peak current generated by the normal operation of the power module after startup is relatively low, and the action threshold of the peak current protection circuit cannot be designed too high. Than limit

In short, not only the capacity of the filter capacitor C1 is required to be large enough to obtain a longer output voltage holding time, but also to ensure that the power module can be started smoothly, the action threshold of the peak current protection circuit must be designed to a higher value, and at this time This situation occurs: when a short circuit or overcurrent occurs at the output load end, the power module cannot achieve reliable and effective protection, and the current through the rectifier diode D1 will still be very large at this time

That is, by increasing the capacity of the filter capacitor, the output voltage of the three-terminal integrated voltage regulator has a longer holding time function. If a special startup circuit design is not adopted on the primary side control circuit, it will be difficult to start the power module. question

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