Starting circuit, series resonance conversion device and switching power supply

Abstract

The invention relates to a starting circuit, a series resonance conversion device and a switching power supply. The starting circuit comprises a controller; a bus capacitor ripple detection unit, a temperature detection unit and an output voltage feedback adjustment unit which are connected with the controller. The temperature detection unit is used for sending a temperature detection signal to the controller; the controller is used for controlling the temperature sensor to detect the ambient temperature when the temperature detection signal judges that the ambient temperature is lower than apreset temperature threshold; a corresponding control mode is set as a pulse width modulation mode; the output voltage feedback adjustment unit is used for generating a feedback adjustment signal andsending the feedback adjustment signal to the controller; the controller is also used for adjusting the duty ratio of the pulse width modulation signal according to the feedback adjustment signal; thebus capacitor ripple detection unit is used for generating ripple voltage detection signals and sending the ripple voltage detection signals to the controller, the controller is further used for adjusting a corresponding control mode into a frequency modulation mode when judging that the bus capacitor ripple voltage is smaller than a preset voltage threshold value, and the starting circuit improves the low-temperature working characteristic of the series resonant converter.

Description

technical field [0001] The invention relates to the field of circuits, in particular to a starting circuit, a series resonant conversion device and a switching power supply. Background technique [0002] In the control process of the current LLC (series resonant converter) circuit, when the power supply is turned on at low temperature and full load, the bus capacitor voltage output by the front stage PFC (Power Factor Correction, power factor correction) will drop at the moment when the output is suddenly fully loaded. Obviously, the lower the ambient temperature, the greater the drop of the bus capacitor voltage with the sudden full load of the output, which will lead to the abnormal shutdown of the LLC circuit converter in the subsequent stage, and it will enter a repeated restart state, and even damage the power supply when the protection setting is unreasonable. . [0003] Therefore, the usual practice is to increase the capacity of the front-stage high-voltage DC bus c...

AI Technical Summary

Problems solved by technology

[0002] In the control process of the current LLC (series resonant converter) circuit, when the power supply is turned on at low temperature and full load, the bus capacitor voltage output by the front stage PFC (Power Factor Correction, power factor correction) will drop at the moment when the output is suddenly fully loaded. Obviously, the lower the ambient temperature, the greater the drop of the bus capacitor voltage with the sudden full load of the output, which will lead to the abnormal shutdown of the LLC circuit converter in the subsequent stage, and it will enter a repeated restart state, and even damage the power supply when the protection setting is unreasonable.

[0003] Therefore, the usual practice is to increase the capacity of the front-stage high-voltage DC bus capacitor to reduce the drop of the bus voltage at the moment of starting, or use multiple bus capacitors in parallel to reduce the influence of the low-temperature bus capacitor ESR to reduce the bus voltage during startup. The instantaneous drop rate will increase the cost and volume of the product accordingly

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