Switching power supply input voltage sampling circuit

Abstract

The utility model discloses an input voltage sampling circuit of a switching power supply, which comprises an input detection module used for reducing the voltage of commercial power, a rectifying and filtering module used for rectifying and filtering the reduced AC voltage into stable DC voltage, and an input voltage sampling module used for collecting the rectified and filtered stable DC voltage, the input end of the input detection module is connected with 220V commercial power, the output end of the input detection module is connected with the input end of the rectification filtering module, and the output end of the rectification filtering module is connected with the input end of the input voltage sampling module. According to the switching power supply input voltage sampling circuit provided by the utility model, the independent input detection module is adopted to carry out voltage reduction on the commercial power, then the commercial power passes through the rectification filtering module, the rectified and filtered voltage is directly sampled, and the independent input detection module is adopted to eliminate the influence of the auxiliary power supply module on the input voltage sampling module. And the stability and the accuracy of an input voltage sampling value are improved.

Description

Technical Field

[0001] The utility model relates to the technical field of switching power supplies, and more specifically to a switching power supply input voltage sampling circuit. Background Art

[0002] At present, the input voltage sampling of the switching power supply usually adopts the method of directly taking power from the auxiliary power supply input terminal, that is, the AC input is stepped down by the auxiliary power supply module, rectified and filtered by the rectifier and filter module, and then the auxiliary power supply is powered. At the same time, the voltage after rectification and filtering is sampled. The operation of the auxiliary power supply will cause inaccurate input voltage sampling values. Utility Model Content

[0003] The technical problem to be solved by the utility model is to provide a switching power supply input voltage sampling circuit to improve the stability and accuracy of the input voltage sampling value.

[0004] In order to solve the above technical problems, the technical solutions adopted by the present utility model are as follows.

[0005] A switching power supply input voltage sampling circuit comprises an input detection module for stepping down the mains, a rectifier and filter module for rectifying and filtering the stepped-down AC voltage into a stable DC voltage, and an input voltage sampling module for collecting the stable DC voltage after rectification and filtering, wherein the input end of the input detection module is connected to the mains 220V, the output end of the input detection module is connected to the input end of the rectifier and filter module, and the output end of the rectifier and filter module is connected to the input end of the input voltage sampling module.

[0006] To further optimize the technical solution, the input detection module includes an input detection transformer, the primary winding of the input detection transformer is connected to the mains 220V, and the secondary winding of the input detection transformer is connected to the input end of the rectifier and filter module.

[0007] To further optimize the technical solution, the rectification and filtering module includes a rectifier bridge connected to the secondary winding of the input detection transformer for rectifying the AC voltage and a filtering capacitor for filtering.

[0008] To further optimize the technical solution, the input voltage sampling module includes an undervoltage sampling branch for outputting an undervoltage sampling signal and an overvoltage sampling branch for outputting an overvoltage sampling signal, the input ends of the undervoltage sampling branch and the overvoltage sampling branch are respectively connected to the output end of the rectifier and filter module, and the output ends of the undervoltage sampling branch and the overvoltage sampling branch are connected to a current limiting resistor.

[0009] To further optimize the technical solution, the undervoltage sampling branch includes a sampling resistor, a filter capacitor, a comparator and a diode connected in series at the output end of the filter and rectifier circuit in sequence, the input end of the sampling resistor is connected to the output end of the filter and rectifier circuit, the output end of the sampling resistor is connected to the negative input end of the comparator, the output end of the comparator is connected to the positive electrode of the diode, the negative electrode of the diode is connected to the current limiting resistor, the positive electrode of the filter capacitor is connected to the negative input end of the comparator, and the negative electrode of the filter capacitor is grounded.

[0010] To further optimize the technical solution, the overvoltage sampling branch includes a sampling resistor, a filter capacitor, a comparator and a diode connected in series at the output end of the filter and rectifier circuit in sequence, the input end of the sampling resistor is connected to the output end of the filter and rectifier circuit, the output end of the sampling resistor is connected to the positive input end of the comparator, the output end of the comparator is connected to the positive electrode of the diode, the negative electrode of the diode is connected to the current limiting resistor, the positive electrode of the filter capacitor is connected to the positive input end of the comparator, and the negative electrode of the filter capacitor is grounded.

[0011] Due to the adoption of the above technical scheme, the technical progress achieved by the present invention is as follows.

[0012] The utility model provides a switching power supply input voltage sampling circuit, which uses an independent input detection module to reduce the voltage of the mains power, and then directly samples the voltage after rectification and filtering through a rectification and filtering module. The use of an independent input detection module can eliminate the influence of the auxiliary power supply module on the input voltage sampling module, thereby improving the stability and accuracy of the input voltage sampling value. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic diagram of the structure of the utility model;

[0014] Figure 2 This is a circuit diagram of the utility model. DETAILED DESCRIPTION

[0015] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0016] A switching power supply input voltage sampling circuit, combined with Figure 1 As shown, it includes an input detection module, a rectifier and filter module and an input voltage sampling module. The input end of the input detection module is connected to the mains 220V, the output end of the input detection module is connected to the input end of the rectifier and filter module, and the output end of the rectifier and filter module is connected to the input end of the input voltage sampling module.

[0017] The circuit diagram of the utility model is as follows Figure 2As shown, the input detection module includes an input detection transformer, which is used to step down the AC power. The primary winding of the input detection transformer is connected to the AC power 220V, and the secondary winding of the input detection transformer is connected to the input end of the rectifier and filter module to convert the input AC220V voltage into AC24V voltage.

[0018] The rectifier and filter module includes a rectifier bridge and a filter capacitor. The rectifier bridge is connected to the secondary winding of the input detection transformer to rectify the AC voltage and the filter circuit performs filtering.

[0019] The input voltage sampling module includes an undervoltage sampling branch and an overvoltage sampling branch. The undervoltage sampling branch is used to output an undervoltage sampling signal, and the overvoltage sampling branch is used to output an overvoltage sampling signal. The input ends of the undervoltage sampling branch and the overvoltage sampling branch are respectively connected to the output end of the rectifier and filter module, and the output ends of the undervoltage sampling branch and the overvoltage sampling branch are connected to the current limiting resistor R146.

[0020] The undervoltage sampling branch includes a sampling resistor, a filter capacitor, a comparator and a diode connected in series at the output end of the filter and rectifier circuit in sequence. The sampling resistors are R118, R141 and R14 connected in series in sequence. The sampling resistor R118 is connected to the output end of the filter and rectifier circuit, the sampling resistor R14 is connected to the negative input end of the comparator N04A, the output end of the comparator N04A is connected to the positive electrode of the diode V40, the negative electrode of the diode V40 is connected to the current limiting resistor R146, the positive electrode of the filter capacitor C14 is connected to the negative input end of the comparator, and the negative electrode of the filter capacitor C14 is grounded.

[0021] The overvoltage sampling branch includes a sampling resistor, a filter capacitor, a comparator and a diode connected in series at the output end of the filter and rectifier circuit. The sampling resistors are R75, R142, R143 and R1 connected in series. The sampling resistor R75 is connected to the output end of the filter and rectifier circuit. The sampling resistor R143 and the resistor R1 are connected in parallel and then connected to the positive input end of the comparator N05A. The output end of the comparator N05A is connected to the positive electrode of the diode V28, and the negative electrode of the diode V28 is connected to the current limiting resistor R146. The positive electrode of the filter capacitor C105 is connected to the positive input end of the comparator, and the negative electrode of the filter capacitor C105 is grounded.

[0022] When the utility model is working, the mains is input, and the input AC220V voltage is converted into AC24V voltage through the input detection transformer, which is rectified and filtered by the rectifier bridge and the filter capacitor. One path is divided by a resistor and enters the voltage comparator for comparison. If it is less than the set value, an input undervoltage protection signal is transmitted to the outside through the diode and the current limiting resistor. The second path is divided by a resistor and enters the voltage comparator for comparison. If it is greater than the set value, an input overvoltage protection signal is transmitted to the outside through the diode and the current limiting resistor.

Claims

1. A switching power supply input voltage sampling circuit, characterized in that: It includes an input detection module for stepping down the mains power, a rectifier and filter module for rectifying and filtering the stepped-down AC voltage into a stable DC voltage, and an input voltage sampling module for collecting the stable DC voltage after rectification and filtering. The input end of the input detection module is connected to the mains power 220V, the output end of the input detection module is connected to the input end of the rectifier and filter module, and the output end of the rectifier and filter module is connected to the input end of the input voltage sampling module.

2. The switching power supply input voltage sampling circuit according to claim 1, characterized in that: The input detection module comprises an input detection transformer, the primary winding of the input detection transformer is connected to the mains 220V, and the secondary winding of the input detection transformer is connected to the input end of the rectifier and filter module.

3. The switching power supply input voltage sampling circuit according to claim 2, characterized in that: The rectification and filtering module comprises a rectifier bridge connected to the secondary winding of the input detection transformer for rectifying the AC voltage and a filtering capacitor for filtering.

4. The switching power supply input voltage sampling circuit according to claim 1, characterized in that: The input voltage sampling module includes an undervoltage sampling branch for outputting an undervoltage sampling signal and an overvoltage sampling branch for outputting an overvoltage sampling signal. The input ends of the undervoltage sampling branch and the overvoltage sampling branch are respectively connected to the output end of the rectifier and filter module, and the output ends of the undervoltage sampling branch and the overvoltage sampling branch are connected to a current-limiting resistor.

5. The switching power supply input voltage sampling circuit according to claim 4, characterized in that: The undervoltage sampling branch includes a sampling resistor, a filter capacitor, a comparator and a diode which are connected in series at the output end of the filter and rectifier circuit in sequence. The input end of the sampling resistor is connected to the output end of the filter and rectifier circuit, the output end of the sampling resistor is connected to the negative input end of the comparator, the output end of the comparator is connected to the positive electrode of the diode, the negative electrode of the diode is connected to the current limiting resistor, the positive electrode of the filter capacitor is connected to the negative input end of the comparator, and the negative electrode of the filter capacitor is grounded.

6. The switching power supply input voltage sampling circuit according to claim 4, characterized in that: The overvoltage sampling branch includes a sampling resistor, a filter capacitor, a comparator and a diode which are connected in series at the output end of the filter and rectifier circuit in sequence. The input end of the sampling resistor is connected to the output end of the filter and rectifier circuit, the output end of the sampling resistor is connected to the positive input end of the comparator, the output end of the comparator is connected to the positive electrode of the diode, the negative electrode of the diode is connected to the current limiting resistor, the positive electrode of the filter capacitor is connected to the positive input end of the comparator, and the negative electrode of the filter capacitor is grounded.

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