Overpower protection circuit for current-type switching power supply
A current-type switch and over-power protection technology, which is applied to emergency protection circuit devices, electrical components, etc., can solve the problems of low resistance value of the sampling resistor 103, heating of the power switch tube, and increased duty cycle, so as to avoid circuit damage The effect of the situation
Active Publication Date: 2013-10-23
成都启臣微电子股份有限公司
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But in the actual situation, there is the following possibility: the sampling resistor 103 is short-circuited or the resistance value is abnormally low. Since the CS terminal voltage is equal to the product of the power switch tube current and the resistance value of the sampling resistor, when the resistance value of the sampling resistor is extremely small or is short-circuited, The CS terminal voltage can no longer reflect the current flowing through the power switch tube normally. Even if the power switch tube current is larger, the CS terminal voltage is still very low. The control loop makes a judgment based on the low CS voltage, so that the PWM signal controls the power switch tube to increase. Large duty cycle, in this over-power state, it is easy to cause the power switch tube to run at the maximum duty cycle for a long time and cannot be adjusted normally, causing a large amount of heat in the power switch tube in a short period of time, causing damage to the power switch tube or other parts of the circuit even explode
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[0035] The specific embodiment of the present invention will be further described in detail below in conjunction with the accompanying drawings.
[0036] The current-type switching power supply overpower protection circuit of the present invention includes a power switch tube current detection terminal, a load state detection terminal and a pulse width modulation signal terminal, and also includes an input overpower detection circuit 201, an input normal power detection circuit 202, and a counting lock circuit, the input overpower detection circuit 201 includes:
[0037] The first judging circuit, its input terminal is connected with the current detection terminal of the power switch tube, and judges whether the current detection terminal of the power switch tube
[0038] Whether the terminal voltage is lower than a preset value V1, and whether the duration of being lower than V1 is greater than a preset duration T1, and output a first judgment signal;
[0039] The maximum du...
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The invention discloses an overpower protection circuit for a current-type switching power supply. The overpower protection circuit comprises a power switch tube current detection end, a load state detection end, a pulse width modulation signal end, an input overpower detection circuit, an input normal power detection circuit and a counting locking circuit, wherein the input overpower detection circuit comprises a first judgement circuit, a maximum duty cycle detection circuit and an AND logical operation circuit. With the adoption of the overpower protection circuit for the current-type switching power supply, disclosed by the invention, a switching duty cycle and a current sampling signal of a power switch tube are monitored simultaneously to judge whether a switching power supply enters an overpower state or not and close the power switch tube in time, thus effectively avoiding the occurrence of a circuit damage situation which possibly occurs after the circuit enters the overpower state due to the abnormal state of the current sampling resistance.
Description
technical field [0001] The invention belongs to the field of integrated circuit design and relates to the design of switching power supply integrated circuits, in particular to a current-type switching power supply overpower protection circuit. Background technique [0002] Switching power supply is a kind of power supply that uses modern power electronic technology to control the time ratio of switching on and off to maintain a stable output voltage. Switching power supply is generally composed of pulse width modulation (PWM) control IC and MOSFET. With the development and innovation of power electronics technology, switching power supply technology is constantly innovating. At present, switching power supply is widely used in almost all electronic devices due to its small size, light weight and high efficiency. It is an indispensable power supply method for the rapid development of today's electronic information industry. [0003] According to the sampling method of the c...
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Inventor 唐波马强许刚颍朱樟明
Owner 成都启臣微电子股份有限公司