Overload protection circuit

Abstract

The utility model relates to an overload protection circuit, comprising a transformation rectification circuit, a current sampling circuit and an overload control circuit, the current sampling circuit is connected with the transformation rectification circuit, and the overload control circuit is respectively connected with the transformation rectification circuit and the current sampling circuit; wherein the current sampling circuit is specifically a circuit which carries out current sampling through a transformer, and the overload control circuit is specifically a circuit which carries out overload control through a silicon controlled rectifier and a triode. The overload protection circuit provided by the utility model samples the current applied to the transformation rectification circuit through the transformer, so that the silicon controlled rectifier is triggered when the sampled current exceeds a preset value, and the triode is cut off when the silicon controlled rectifier is conducted, thereby interrupting the output of the transformation rectification circuit and forming overload protection. The rated power of the power supply is in a safe range.

Description

Technical Field

[0001] The utility model relates to the field of electronic circuits, and specifically designs an overload protection circuit. Background Art

[0002] Most of the existing high-voltage transistor power supplies use limiting circuits as short-circuit protection. However, since excessive current and voltage quickly exceed the rated power of the control transistor, the existing limiting circuits are not applicable. Utility Model Content

[0003] The utility model provides an overload protection circuit, which can perform overload protection on a power supply and ensure that the rated power of the power supply is within a safe range.

[0004] The utility model provides a technical solution to the above technical problem as follows: an overload protection circuit, comprising a transformer and rectifier circuit, a current sampling circuit and an overload control circuit, wherein the current sampling circuit is connected to the transformer and rectifier circuit, and the overload control circuit is respectively connected to the transformer and rectifier circuit and the current sampling circuit; wherein the current sampling circuit is specifically a circuit for current sampling through a transformer, and the overload control circuit is specifically a circuit for overload control through a thyristor and a triode.

[0005] On the basis of the above technical solution, the present invention can also be improved as follows.

[0006] Furthermore, the transformer-rectifier circuit includes: a first transformer and a rectifier circuit; one end of the secondary coil of the first transformer is connected to an input end of the rectifier circuit, the other end of the secondary coil of the first transformer is connected to the other input end of the rectifier circuit through the current sampling circuit, and two output ends of the rectifier circuit are connected to the overload control circuit.

[0007] Further, the rectifier circuit comprises:

[0008] a first diode, wherein the positive electrode is connected to one end of the secondary coil of the first transformer, and the negative electrode is connected to the overload control circuit;

[0009] a second diode, a cathode of which is connected to one end of the secondary coil of the first transformer, and a cathode of which is connected to the overload control circuit;

[0010] a third diode, a cathode of which is connected to the cathode of the first diode, and a cathode of which is connected to the other end of the secondary coil of the first transformer through the current sampling circuit;

[0011] a fourth diode, a cathode connected to the anode of the third diode, and an anode connected to the anode of the second diode;

[0012] Among them, the anode of the first diode and the cathode of the second diode together constitute an input end of the rectifier circuit, and the anode of the third diode and the cathode of the fourth diode together constitute another input end of the rectifier circuit; the cathode of the first diode and the cathode of the third diode together constitute an output end of the rectifier circuit, and the anode of the second diode and the cathode of the fourth diode together constitute another output end of the rectifier circuit.

[0013] Further, the overload control circuit comprises:

[0014] a fifth resistor, one end of which is connected to an output end of the rectifier circuit;

[0015] A first resistor, one end of which is connected to the other end of the fifth resistor;

[0016] A thyristor, a positive electrode of which is connected to the other end of the first resistor, and a negative electrode of which is connected to the other output end of the rectifier circuit;

[0017] A second capacitor, one end of which is connected to the other output end of the rectifier circuit;

[0018] A first triode, a base connected to the other end of the second capacitor; and a collector connected to the other end of the fifth resistor;

[0019] The second transistor has a base connected to the emitter of the first transistor and a collector connected to the other end of the fifth resistor.

[0020] Furthermore, the overload control circuit further includes:

[0021] The first capacitor has one end connected to the other end of the fifth resistor, and the other end connected to the other output end of the rectifier circuit.

[0022] Furthermore, the current sampling circuit comprises:

[0023] a second transformer, one end of the primary coil of which is connected to the other end of the secondary coil of the first transformer, and the other end of the primary coil of which is connected to the other input end of the rectifier circuit;

[0024] A third resistor has one end connected to the control electrode of the thyristor and one end of the secondary coil of the second transformer, and the other end connected to the negative electrode of the thyristor and the other end of the secondary coil of the second transformer.

[0025] Furthermore, the current sampling circuit further includes:

[0026] A third capacitor is connected in parallel with the third resistor.

[0027] Furthermore, the invention further includes a first recovery circuit, wherein the first recovery circuit includes:

[0028] The switch has two ends connected to the positive electrode and the negative electrode of the thyristor respectively.

[0029] Furthermore, a second recovery circuit is included, wherein the second recovery circuit includes:

[0030] The third triode;

[0031] a fourth resistor, one end of which is connected to the emitter of the third triode, and the other end of which is connected to the negative electrode of the thyristor;

[0032] a seventh resistor, one end of which is connected to the collector of the third triode;

[0033] a sixth resistor, one end of which is connected to the other end of the seventh resistor, and the other end of which is connected to the base of the first transistor;

[0034] a second resistor, one end of which is connected to the other end of the seventh resistor, and the other end of which is connected to the other end of the first resistor;

[0035] a fifth diode, a cathode connected to the other end of the first resistor, and an anode connected to the emitter of the second transistor;

[0036] A sixth diode has a cathode connected to the emitter of the second transistor and an anode connected to the emitter of the third transistor.

[0037] Furthermore, the models of the first transistor, the second transistor and the third transistor are 2N3442, 2N3442 and 2N2095 respectively.

[0038] The beneficial effect of the utility model is that an overload protection circuit of the utility model samples the current added to the transformer rectifier circuit through a transformer, so that when the sampled current exceeds a predetermined value, the thyristor is triggered, and when the thyristor is turned on, the triode is cut off, so that the output of the transformer rectifier circuit is interrupted, thereby forming an overload protection and ensuring that the rated power of the power supply is within a safe range. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a structural block diagram of an overload protection circuit of the utility model;

[0040] Figure 2 The utility model is a schematic diagram of an overload protection circuit. DETAILED DESCRIPTION

[0041] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0042] like Figure 1As shown, an overload protection circuit includes a transformer and rectifier circuit, a current sampling circuit and an overload control circuit, wherein the current sampling circuit is connected to the transformer and rectifier circuit, and the overload control circuit is connected to the transformer and rectifier circuit and the current sampling circuit respectively; wherein the current sampling circuit is specifically a circuit for current sampling through a transformer, and the overload control circuit is specifically a circuit for overload control through a thyristor and a triode.

[0043] The utility model discloses an overload protection circuit which samples the current added to the transformer rectifier circuit through the transformer in the current sampling circuit, so that when the sampled current exceeds a preset value, the thyristor SCR in the overload control circuit is triggered, and when the thyristor SCR is turned on, the triode in the overload control circuit is cut off, so that the output of the transformer rectifier circuit is interrupted, thereby forming overload protection and ensuring that the rated power of the power supply is within a safe range.

[0044] In this specific embodiment, Figure 2 As shown, the transformer-rectifier circuit includes: a first transformer T1 and a rectifier circuit; one end of the secondary coil of the first transformer T1 is connected to an input end of the rectifier circuit, the other end of the secondary coil of the first transformer T1 is connected to the other input end of the rectifier circuit through the current sampling circuit, and the two output ends of the rectifier circuit are connected to the overload control circuit.

[0045] Preferably, the rectifier circuit comprises:

[0046] a first diode D1, the anode of which is connected to one end of the secondary coil of the first transformer T1, and the cathode of which is connected to the overload control circuit;

[0047] a second diode D2, a cathode of which is connected to one end of the secondary coil of the first transformer T1, and a cathode of which is connected to the overload control circuit;

[0048] a third diode D3, a cathode connected to the cathode of the first diode D1, and a cathode connected to the other end of the secondary coil of the first transformer T1 through the current sampling circuit;

[0049] a fourth diode D4, a cathode connected to the anode of the third diode D3, and an anode connected to the anode of the second diode D2;

[0050] Among them, the anode of the first diode D1 and the cathode of the second diode D2 form an input end of the rectifier circuit, and the anode of the third diode D3 and the cathode of the fourth diode D4 form another input end of the rectifier circuit; the cathode of the first diode D1 and the cathode of the third diode D3 form an output end of the rectifier circuit, and the anode of the second diode D2 and the cathode of the fourth diode D4 form another output end of the rectifier circuit.

[0051] In this specific embodiment, Figure 2 As shown, the overload control circuit includes:

[0052] a fifth resistor R5, one end of which is connected to an output end of the rectifier circuit;

[0053] A first resistor R1, one end of which is connected to the other end of the fifth resistor R5;

[0054] A thyristor SCR, a positive electrode connected to the other end of the first resistor R1, and a negative electrode connected to the other output end of the rectifier circuit;

[0055] A second capacitor C2, one end of which is connected to the other output end of the rectifier circuit;

[0056] A first transistor Q1, a base connected to the other end of the second capacitor C2; and a collector connected to the other end of the fifth resistor R5;

[0057] The second transistor Q2 has a base connected to the emitter of the first transistor Q1 , and a collector connected to the other end of the fifth resistor R5 .

[0058] Preferably, the overload control circuit further includes:

[0059] The first capacitor C1 has one end connected to the other end of the fifth resistor R5 , and the other end connected to the other output end of the rectifier circuit.

[0060] The first capacitor C1 is used to filter the voltage output by the rectifier circuit.

[0061] In this specific embodiment, Figure 2 As shown, the current sampling circuit includes:

[0062] A second transformer T2, one end of the primary coil of which is connected to the other end of the secondary coil of the first transformer T1, and the other end of the primary coil of which is connected to the other input end of the rectifier circuit;

[0063] The third resistor R3 has one end connected to the control electrode of the thyristor SCR and one end of the secondary coil of the second transformer T2, and the other end connected to the negative electrode of the thyristor SCR and the other end of the secondary coil of the second transformer T2.

[0064] Preferably, the current sampling circuit further includes:

[0065] The third capacitor C3 is connected in parallel with the third resistor R3.

[0066] The third capacitor C3 is used to filter the voltage across the third resistor R3 to ensure the stability of sampling.

[0067] In this specific embodiment, Figure 2 As shown, a first recovery circuit is also included, and the first recovery circuit includes:

[0068] The switch K has two ends connected to the positive electrode and the negative electrode of the thyristor SCR respectively.

[0069] In this specific embodiment, Figure 2 As shown, a second recovery circuit is also included, and the second recovery circuit includes:

[0070] The third transistor Q3;

[0071] a fourth resistor, one end of which is connected to the emitter of the third transistor Q3, and the other end of which is connected to the negative electrode of the thyristor SCR;

[0072] a seventh resistor R7, one end of which is connected to the collector of the third transistor Q3;

[0073] a sixth resistor R6, one end of which is connected to the other end of the seventh resistor R7, and the other end of which is connected to the base of the first transistor Q1;

[0074] A second resistor R2, one end of which is connected to the other end of the seventh resistor R7, and the other end of which is connected to the other end of the first resistor R1;

[0075] a fifth diode D5, a cathode connected to the other end of the first resistor R1, and an anode connected to the emitter of the second transistor Q2;

[0076] The sixth diode D6 has a cathode connected to the emitter of the second transistor Q2 and an anode connected to the emitter of the third transistor Q3.

[0077] Among them, after the overload protection, the switch K in the first recovery circuit can be manually pressed to remove the holding current of the thyristor SCR, thereby restoring the current in the overload protection circuit; or the input voltage can be cut off by outputting a control signal at the base of the third transistor Q3 in the second recovery circuit, thereby removing the holding current of the thyristor SCR, thereby restoring the current in the overload protection circuit.

[0078] In this specific embodiment, the models of the first transistor Q1, the second transistor Q2 and the third transistor Q3 are 2N3442, 2N3442 and 2N2095 respectively; the capacitances of the first capacitor C1, the second capacitor C2 and the third capacitor C3 are 1uf, 0.1uf and 1uf respectively. The models of the fifth diode D5 and the sixth diode D6 are 1N758 and 1N758 respectively. The resistances of the first resistor R1, the second resistor R2, the third resistor R3, the fourth resistor R4, the fifth resistor R5, the sixth resistor R6 and the seventh resistor R7 are 10KΩ, 2KΩ, 10KΩ, 20KΩ, 10Ω, 5Ω and 1Ω respectively.

[0079] In an overload protection circuit of the utility model, the current added to the transformer rectifier circuit is sampled through the second transformer T2, and a voltage drop is generated on the third resistor R3, so that the thyristor SCR is triggered when the sampled current exceeds a predetermined value. When a current overload occurs, the additional voltage generated on the third resistor R3 triggers the thyristor SCR to turn it on. When the thyristor SCR is turned on, there is no current on the base of the first transistor Q1 and the second transistor Q2, so the first transistor Q1 and the second transistor Q2 are both cut off, thereby interrupting the output of the transformer rectifier circuit, thereby forming an overload protection to ensure that the rated power of the power supply is within a safe range.

[0080] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An overload protection circuit, characterized in that: It includes a transformer and rectifier circuit, a current sampling circuit and an overload control circuit, wherein the current sampling circuit is connected to the transformer and rectifier circuit, and the overload control circuit is respectively connected to the transformer and rectifier circuit and the current sampling circuit; wherein the current sampling circuit is specifically a circuit for current sampling through a transformer, and the overload control circuit is specifically a circuit for overload control through a thyristor and a triode.

2. The overload protection circuit according to claim 1, characterized in that: The transformer-rectifier circuit includes: a first transformer and a rectifier circuit; one end of the secondary coil of the first transformer is connected to an input end of the rectifier circuit, the other end of the secondary coil of the first transformer is connected to the other input end of the rectifier circuit through the current sampling circuit, and the two output ends of the rectifier circuit are connected to the overload control circuit.

3. The overload protection circuit according to claim 2, characterized in that: The rectifier circuit comprises: a first diode, wherein the positive electrode is connected to one end of the secondary coil of the first transformer, and the negative electrode is connected to the overload control circuit; a second diode, a cathode of which is connected to one end of the secondary coil of the first transformer, and a cathode of which is connected to the overload control circuit; a third diode, a cathode of which is connected to the cathode of the first diode, and a cathode of which is connected to the other end of the secondary coil of the first transformer through the current sampling circuit; a fourth diode, a cathode connected to the anode of the third diode, and an anode connected to the anode of the second diode; Among them, the anode of the first diode and the cathode of the second diode together constitute an input end of the rectifier circuit, and the anode of the third diode and the cathode of the fourth diode together constitute another input end of the rectifier circuit; the cathode of the first diode and the cathode of the third diode together constitute an output end of the rectifier circuit, and the anode of the second diode and the cathode of the fourth diode together constitute another output end of the rectifier circuit.

4. The overload protection circuit according to claim 2, characterized in that: The overload control circuit comprises: a fifth resistor, one end of which is connected to an output end of the rectifier circuit; a first resistor, one end of which is connected to the other end of the fifth resistor; A thyristor, a positive electrode of which is connected to the other end of the first resistor, and a negative electrode of which is connected to the other output end of the rectifier circuit; A second capacitor, one end of which is connected to the other output end of the rectifier circuit; A first triode, a base connected to the other end of the second capacitor; and a collector connected to the other end of the fifth resistor; The second transistor has a base connected to the emitter of the first transistor and a collector connected to the other end of the fifth resistor.

5. The overload protection circuit according to claim 4, characterized in that: The overload control circuit also includes: The first capacitor has one end connected to the other end of the fifth resistor, and the other end connected to the other output end of the rectifier circuit.

6. The overload protection circuit according to claim 4, characterized in that: The current sampling circuit comprises: a second transformer, one end of the primary coil of which is connected to the other end of the secondary coil of the first transformer, and the other end of the primary coil of which is connected to the other input end of the rectifier circuit; A third resistor has one end connected to the control electrode of the thyristor and one end of the secondary coil of the second transformer, and the other end connected to the negative electrode of the thyristor and the other end of the secondary coil of the second transformer.

7. The overload protection circuit according to claim 6, characterized in that: The current sampling circuit also includes: A third capacitor is connected in parallel with the third resistor.

8. The overload protection circuit according to claim 6, characterized in that: Also included is a first recovery circuit, the first recovery circuit comprising: The switch has two ends connected to the positive electrode and the negative electrode of the thyristor respectively.

9. The overload protection circuit according to claim 6, characterized in that: Also included is a second recovery circuit, the second recovery circuit comprising: The third triode; a fourth resistor, one end of which is connected to the emitter of the third triode, and the other end of which is connected to the negative electrode of the thyristor; a seventh resistor, one end of which is connected to the collector of the third triode; a sixth resistor, one end of which is connected to the other end of the seventh resistor, and the other end of which is connected to the base of the first transistor; a second resistor, one end of which is connected to the other end of the seventh resistor, and the other end of which is connected to the other end of the first resistor; a fifth diode, a cathode connected to the other end of the first resistor, and an anode connected to the emitter of the second transistor; A sixth diode has a cathode connected to the emitter of the second transistor and an anode connected to the emitter of the third transistor.

10. The overload protection circuit according to claim 9, characterized in that: Models of the first transistor, the second transistor and the third transistor are 2N3442, 2N3442 and 2N2095 respectively.

Images