CN211046467U - Protection circuit of double-tube forward conversion circuit - Google Patents
Protection circuit of double-tube forward conversion circuit Download PDFInfo
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- CN211046467U CN211046467U CN201922122848.2U CN201922122848U CN211046467U CN 211046467 U CN211046467 U CN 211046467U CN 201922122848 U CN201922122848 U CN 201922122848U CN 211046467 U CN211046467 U CN 211046467U
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Abstract
The utility model discloses a protection circuit of a double-tube forward conversion circuit, when an invalidation short circuit exists in an upper power switch tube and a lower power switch tube, when entering a follow current state, the sampling output current of a current detection device is 0, so that the voltage at two ends of a second resistor is 0V, and then the protection circuit can enter a protection state, thereby protecting the other devices from being damaged; when the upper clamping diode and the lower clamping diode are failed and short-circuited, the protection is carried out by detecting the voltage at two ends of the first resistor. The protection circuit of the double-tube forward conversion circuit not only detects a forward current signal flowing through the direct-current bus, but also simultaneously detects a reverse follow current signal flowing through the direct-current bus, so that the protection circuit not only can quickly respond to the failure short circuit of the upper clamping diode and the lower clamping diode, but also can quickly respond to the failure short circuit of the upper power switch tube and the lower power switch tube.
Description
Technical Field
The utility model relates to a double-barrelled just swashing converting circuit, in particular to double-barrelled just swashing converting circuit's protection circuit.
Background
The two-transistor forward converter circuit is composed of two power switching transistors Q1 and Q2, two clamping diodes D1 and D2, and a transformer T1, as shown in fig. 1.
When the two power switching tubes Q1 and Q2 are simultaneously conducted, a forward voltage is formed on the primary side of the transformer T1, and when the forward voltage flows through the current on the primary side of the transformer T1, the current flows from top to bottom, and the transformer transmits energy to the secondary side; when the two power switching tubes Q1 and Q2 are turned off at the same time, the current flowing through the primary side of the transformer T1 continues to flow from top to bottom, both the two clamping diodes D1 and D2 are turned on, the primary side of the transformer T1 forms a reverse voltage, and the magnetic field of the transformer T1 is in a reset state.
The failure modes of the power switching tubes Q1 and Q2 are short circuits. In the two-transistor forward converter circuit, when the power switching transistors Q1 and Q2 fail, in order to prevent further damage to other devices, a protection circuit generally used at present is shown in fig. 2, a current detection device S1 detects a current flowing through a dc bus, and when a certain value is exceeded, a power supply is turned off or the driving of the two power switching transistors Q1 and Q2 is turned off. When one of the two clamping diodes D1, D2 fails (the failure mode is short circuit), the two power switching tubes Q1, Q2 are turned on simultaneously, which causes direct short circuit of the dc power source VCC, and the current flowing through the dc bus rapidly increases, that is, the bus sampling current Id rapidly increases, and when the current exceeds a set value, the protection circuit enters a protection state.
As shown in fig. 3, when the upper power switch Q1 fails and is shorted (T1), the lower power switch Q2 is in a conducting state, the two-transistor forward converter circuit works normally, and the protection circuit does not work at this time, when the lower power switch Q2 is turned off, the primary side current of the transformer T1 flows from top to bottom, flows through the lower power switch Q2 and the lower clamping diode D2 (no dc bus flows, and no current can be detected by the current detection device S1), so that the primary side voltage of the transformer is clamped at 0V, the transformer cannot be normally reset, and after several cycles (the number of cycles is related to the design margin of the transformer), the lower power switch Q2 is turned on again when the transformer is saturated (T2), and the current flowing through the dc bus becomes larger as the saturation level becomes larger, and when the current reaches the protection point (T3), the protection circuit starts to work. The failure short-circuit analysis method, the process and the result of the lower power switch tube Q2 are similar.
As can be seen from the above analysis, in the protection circuit of the conventional two-transistor forward converter circuit, when any one of the clamping diodes D1, D2 fails, the protection circuit can quickly respond to the failure and enter a protection state, but when any one of the power switching transistors Q1, Q2 fails, the response speed of the protection circuit is delayed for several cycles, so that the protection circuit cannot quickly respond, and other devices bear a large pressure, which may cause the failure.
SUMMERY OF THE UTILITY MODEL
The to-be-solved technical problem of the utility model is to provide a double-barrelled forward converter's protection circuit, can not only quick response go up the clamp diode, down the clamp diode short circuit that becomes invalid, can also quick response go up power switch tube, lower power switch tube's the short circuit that becomes invalid.
In order to solve the above technical problem, the utility model provides a protection circuit of double-barrelled forward converter circuit, it includes power switch Q1, lower power switch Q2, goes up clamping diode D1, lower clamping diode D2, transformer T1 and switch tube drive controller;
the input end of the upper power switch tube Q1 and the negative end of the upper clamping diode D1 are connected with a direct current working power supply positive VCC through a positive direct current bus;
the output end of the lower power switch tube Q2 and the positive end of the lower clamping diode D2 are connected with the working ground through a negative direct current bus;
the output end of the upper power switch tube Q1 is connected with the negative end of a lower clamping diode D2 and the upper end of the primary coil of a transformer T1;
the input end of the lower power switch tube Q2 is connected with the positive end of an upper clamping diode D1 and the lower end of the primary coil of a transformer T1;
the protection circuit comprises a current detection device S1, a third diode D3, a fourth diode D4, a first resistor R1 and a second resistor R2;
the current detection device S1 is used for sampling the current flowing through the direct current bus;
the positive terminal of the current detection device S1 is connected with the positive terminal of a third diode D3 and the negative terminal of a fourth diode D4;
the second resistor R2 and the fourth diode D4 are connected in series between the negative terminal and the positive terminal of the current detection device S1;
the first resistor R1 and the third diode D3 are connected in series between the negative terminal and the positive terminal of the current detection device S1;
when the current of the dc bus flows from the working power supply positive VCC to the working ground through the dc bus, the current output from the positive terminal of the current detection device S1 flows to the negative terminal thereof through the third diode D3 and the first resistor R1;
when the current of the dc bus is flowing from the dc bus to the working power supply positive VCC, the current outputted from the negative terminal of the current detection device S1 flows through the second resistor R2 and the fourth diode D4 to the positive terminal thereof;
the switch tube driving controller is used for sending PWM signals to the control ends of the upper power switch tube Q1 and the lower power switch tube Q2 and controlling the upper power switch tube Q1 and the lower power switch tube Q2 to be switched on or switched off simultaneously; when the upper power switch tube Q1 and the lower power switch tube Q2 are controlled to be turned off simultaneously, if the voltage Vr at two ends of the second resistor R2 is 0, the switch tube driving controller outputs a protection signal to enable the double-tube forward conversion circuit to enter a protection state; when the upper power switch Q1 and the lower power switch Q2 are controlled to be turned on simultaneously, if the voltage Vd across the first resistor R1 is greater than the set voltage, the switching tube driving controller outputs a protection signal to make the two-transistor forward conversion circuit enter a protection state.
Preferably, when the switching tube driving controller outputs the protection signal, the dc bus is controlled to be disconnected, the dc working power supply is controlled to be turned off, or the PWM signal is controlled to stop being output to the upper power switching tube Q1 and the lower power switching tube Q2.
Preferably, the first resistor R1 is smaller than the second resistor R2.
Preferably, the resistance of the first resistor R1 is 0.1 Ω -10 Ω.
Preferably, the resistance of the second resistor R2 is 10 Ω -1K Ω.
Preferably, the upper power switch Q1 and the lower power switch Q2 are MOSFETs.
Preferably, the MOSFET is of an N type;
the drain terminal of the MOSFET is used as an input terminal, the source terminal is used as an output terminal, and the gate terminal is used as a control terminal.
Preferably, the MOSFET is of a P type;
the source end of the MOSFET is used as an input end, the drain end is used as an output end, and the gate end is used as a control end.
Preferably, the upper power switch Q1 and the lower power switch Q2 are both IGBTs.
Preferably, the set voltage is 0.2V, 0.5V, or 1V;
the current detection device S1 is used for sampling the current flowing through the negative direct current bus or sampling the current flowing through the positive direct current bus;
the double-tube forward conversion circuit is a double-tube forward conversion circuit of the inverter welding machine.
The utility model discloses a protection circuit of double-barrelled just swashing converting circuit, when last power switch Q1, lower power switch Q2 were closed simultaneously, the electric current that flows through transformer T1 primary coil continued from last down flowing, and last clamping diode D1, lower clamping diode D2 all switch on, and the electric current that flows through the direct current generating line is opposite when last power switch Q1, lower power switch Q2 switched on simultaneously; when one of the upper power switch tube Q1 and the lower power switch tube Q2 is in failure short circuit, and when the current-continuing state (the reset state of the transformer) is entered, the sampling output current of the current detection device is 0, so that the voltage Vr at the two ends of the second resistor R2 is 0V, and at the moment, the protection state can be entered, so that the rest devices are protected from being damaged; when the upper clamping diode D1 and the lower clamping diode D2 fail and are short-circuited, protection can be carried out by detecting the voltage Vd across the first resistor R1. The protection circuit of the double-transistor forward conversion circuit not only detects a forward current signal flowing through a direct-current bus, but also simultaneously detects a reverse follow current signal flowing through the direct-current bus, so that the protection circuit not only can quickly respond to the failure short circuit of the upper clamping diode D1 and the lower clamping diode D2, but also can quickly respond to the failure short circuit of the upper power switch tube Q1 and the lower power switch tube Q2.
Drawings
In order to more clearly illustrate the technical solution of the present invention, the drawings required for the present invention are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a two-transistor forward converter circuit;
FIG. 2 is a protection circuit of a conventional two-transistor forward converter circuit;
FIG. 3 is a waveform diagram of a bus sampling current of a protection circuit of a prior art two-transistor forward converter circuit;
fig. 4 is a circuit diagram of an embodiment of a protection circuit of a double-transistor forward converter circuit according to the present invention.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are only some embodiments, but not all embodiments, of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by a person of ordinary skill in the art without creative efforts belong to the protection scope of the present invention.
Example one
As shown in fig. 4, the protection circuit of the two-transistor forward converter circuit includes an upper power switch Q1, a lower power switch Q2, an upper clamp diode D1, a lower clamp diode D2, a transformer T1 and a switch transistor driving controller;
the input end of the upper power switch tube Q1 and the negative end of the upper clamping diode D1 are connected with a direct current working power supply positive VCC through a positive direct current bus;
the output end of the lower power switch tube Q2 and the positive end of the lower clamping diode D2 are connected with the working ground through a negative direct current bus;
the output end of the upper power switch tube Q1 is connected with the negative end of a lower clamping diode D2 and the upper end of the primary coil of a transformer T1;
the input end of the lower power switch tube Q2 is connected with the positive end of an upper clamping diode D1 and the lower end of the primary coil of a transformer T1;
the protection circuit comprises a current detection device S1, a third diode D3, a fourth diode D4, a first resistor R1 and a second resistor R2;
the current detection device S1 is used for sampling the current flowing through the direct current bus;
the positive terminal of the current detection device S1 is connected with the positive terminal of a third diode D3 and the negative terminal of a fourth diode D4;
the second resistor R2 and the fourth diode D4 are connected in series between the negative terminal and the positive terminal of the current detection device S1;
the first resistor R1 and the third diode D3 are connected in series between the negative terminal and the positive terminal of the current detection device S1;
when the current of the dc bus flows from the working power supply positive VCC to the working ground through the dc bus, the current output from the positive terminal of the current detection device S1 flows to the negative terminal thereof through the third diode D3 and the first resistor R1;
when the current of the dc bus is flowing from the dc bus to the working power supply positive VCC, the current outputted from the negative terminal of the current detection device S1 flows through the second resistor R2 and the fourth diode D4 to the positive terminal thereof;
the switch tube driving controller is used for sending PWM (pulse width control) signals to the control ends of the upper power switch tube Q1 and the lower power switch tube Q2 and controlling the upper power switch tube Q1 and the lower power switch tube Q2 to be switched on or switched off simultaneously; when the upper power switch tube Q1 and the lower power switch tube Q2 are controlled to be turned off simultaneously, if the voltage Vr at two ends of the second resistor R2 is 0, the switch tube driving controller outputs a protection signal to enable the double-tube forward conversion circuit to enter a protection state; when the upper power switch Q1 and the lower power switch Q2 are controlled to be turned on simultaneously, if the voltage Vd across the first resistor R1 is greater than the set voltage, the switching tube driving controller outputs a protection signal to make the two-transistor forward conversion circuit enter a protection state.
In the protection circuit of the dual-transistor forward converter circuit according to the first embodiment, the current detection device S1 samples a current flowing through the dc bus, and when the current of the dc bus flows from the working power supply positive VCC to the working ground, the current output from the positive terminal of the current detection device S1 flows to the negative terminal thereof through the third diode D3 and the first resistor R1, so that a voltage is generated across the first resistor R1; when the current of the dc bus flows from the ground to the positive VCC of the working power supply, the current outputted from the negative terminal of the current detection device S1 flows through the second resistor R2 and the fourth diode D4 to the positive terminal thereof, and a voltage is generated across the second resistor R2; when the upper power switch tube Q1 and the lower power switch tube Q2 are controlled to be turned off simultaneously, if the voltage Vr at the two ends of the second resistor R2 is 0, the switch tube driving controller outputs a protection signal to enable the double-tube forward conversion circuit to enter a protection state; when the upper power switch Q1 and the lower power switch Q2 are controlled to be turned on simultaneously, if the voltage Vd across the first resistor R1 is greater than the set voltage, the switching tube driving controller outputs a protection signal to make the two-transistor forward conversion circuit enter a protection state.
In the protection circuit of the double-transistor forward converter circuit according to the first embodiment, when the upper power switch Q1 and the lower power switch Q2 are turned off at the same time, the current flowing through the primary coil of the transformer T1 continues to flow from top to bottom, the upper clamping diode D1 and the lower clamping diode D2 are both turned on, and the current flowing through the dc bus is opposite to the current flowing through the upper power switch Q1 and the lower power switch Q2 when they are turned on at the same time; when one of the upper power switch tube Q1 and the lower power switch tube Q2 is in failure short circuit, and when the current-continuing state (the reset state of the transformer) is entered, the sampling output current of the current detection device is 0, so that the voltage Vr at the two ends of the second resistor R2 is 0V, and at the moment, the protection state can be entered, so that the rest devices are protected from being damaged; when the upper clamping diode D1 and the lower clamping diode D2 fail and are short-circuited, protection can be carried out by detecting the voltage Vd across the first resistor R1. The protection circuit of the double-transistor forward conversion circuit not only detects a forward current signal flowing through a direct-current bus, but also simultaneously detects a reverse follow current signal flowing through the direct-current bus, so that the protection circuit not only can quickly respond to the failure short circuit of the upper clamping diode D1 and the lower clamping diode D2, but also can quickly respond to the failure short circuit of the upper power switch tube Q1 and the lower power switch tube Q2.
Example two
Based on the protection circuit of the first embodiment of the two-transistor forward converter circuit, when the switching tube driving controller outputs the protection signal, the dc bus is controlled to be disconnected, the dc working power supply is controlled to be turned off, or the PWM signal is controlled to be stopped being output to the upper power switching tube Q1 and the lower power switching tube Q2, so that the two-transistor forward converter circuit enters a protection state.
Preferably, the first resistor R1 is smaller than the second resistor R2.
Preferably, the resistance of the first resistor R1 is 0.1 Ω -10 Ω.
Preferably, the resistance of the second resistor R2 is 10 Ω -1K Ω.
Preferably, the upper power switch Q1 and the lower power switch Q2 are both MOSFETs or IGBTs.
Preferably, the MOSFET is of an N type;
the drain terminal of the MOSFET is used as an input terminal, the source terminal is used as an output terminal, and the gate terminal is used as a control terminal.
Preferably, the MOSFET is of a P type;
the source end of the MOSFET is used as an input end, the drain end is used as an output end, and the gate end is used as a control end.
Preferably, the set voltage is 0.2V, 0.5V, or 1V.
Preferably, the current detection device S1 is used for sampling the current flowing through the negative dc bus or sampling the current flowing through the positive dc bus.
Preferably, the double-transistor forward conversion circuit is a double-transistor forward conversion circuit of an inverter welding machine.
The above description is only a preferred embodiment of the present invention, and should not be taken as limiting the invention, and any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. The protection circuit of the double-transistor forward conversion circuit is characterized by comprising an upper power switch transistor (Q1), a lower power switch transistor (Q2), an upper clamping diode (D1), a lower clamping diode (D2), a transformer (T1) and a switch transistor drive controller;
the input end of the upper power switch tube (Q1) and the negative end of the upper clamping diode (D1) are connected with a direct current working power supply positive (VCC) through a positive direct current bus;
the output end of the lower power switch tube (Q2) and the positive end of the lower clamping diode (D2) are connected with the working ground through a negative direct current bus;
the output end of the upper power switch tube (Q1) is connected with the negative end of the lower clamping diode (D2) and the upper end of the primary coil of the transformer (T1);
the input end of the lower power switch tube (Q2) is connected with the positive end of the upper clamping diode (D1) and the lower end of the primary coil of the transformer (T1);
the protection circuit includes a current detection device (S1), a third diode (D3), a fourth diode (D4), a first resistor (R1), and a second resistor (R2);
the current detection device (S1) is used for sampling the current flowing through the direct current bus;
the positive terminal of the current detection device (S1) is connected with the positive terminal of a third diode (D3) and the negative terminal of a fourth diode (D4);
the second resistor (R2) and the fourth diode (D4) are connected between the negative end and the positive end of the current detection device (S1) in series;
the first resistor (R1) and the third diode (D3) are connected in series between the negative end and the positive end of the current detection device (S1);
when the current of the direct current bus flows from a working power supply positive terminal (VCC) to a working ground through the direct current bus, the current output by the positive terminal of the current detection device (S1) flows to the negative terminal of the current detection device through the third diode (D3) and the first resistor (R1);
when the current of the direct current bus flows from the operation to the positive (VCC) of the operation power supply through the direct current bus, the current output by the negative terminal of the current detection device (S1) flows to the positive terminal thereof through the second resistor (R2) and the fourth diode (D4);
the switch tube driving controller is used for sending PWM signals to the control ends of the upper power switch tube (Q1) and the lower power switch tube (Q2) and controlling the upper power switch tube (Q1) and the lower power switch tube (Q2) to be switched on or switched off simultaneously; when the upper power switch tube (Q1) and the lower power switch tube (Q2) are controlled to be turned off simultaneously, if the voltage (Vr) at two ends of the second resistor (R2) is 0, the switch tube driving controller outputs a protection signal to enable the double-transistor forward conversion circuit to enter a protection state; when the upper power switch tube (Q1) and the lower power switch tube (Q2) are controlled to be conducted simultaneously, if the voltage (Vd) at two ends of the first resistor (R1) is larger than the set voltage, the switch tube driving controller outputs a protection signal to enable the double-tube forward conversion circuit to enter a protection state.
2. The protection circuit of a double-transistor forward converter circuit according to claim 1,
when the switching tube driving controller outputs a protection signal, the direct current bus is controlled to be disconnected, the direct current working power supply is controlled to be turned off, or the PWM signal is controlled to be stopped to be output to the upper power switching tube (Q1) and the lower power switching tube (Q2).
3. The protection circuit of a double-transistor forward converter circuit according to claim 1,
the first resistance (R1) is less than the second resistance (R2).
4. The protection circuit of a double-transistor forward converter circuit according to claim 1,
the first resistor (R1) has a resistance value of 0.1-10 omega.
5. The protection circuit of a double-transistor forward converter circuit according to claim 1,
the resistance value of the second resistor (R2) is 10 omega-1K omega.
6. The protection circuit of a double-transistor forward converter circuit according to claim 1,
the upper power switch tube (Q1) and the lower power switch tube (Q2) are both MOSFETs.
7. The protection circuit of a double-transistor forward converter circuit according to claim 6,
the MOSFET is of an N type;
the drain terminal of the MOSFET is used as an input terminal, the source terminal is used as an output terminal, and the gate terminal is used as a control terminal.
8. The protection circuit of a double-transistor forward converter circuit according to claim 6,
the MOSFET is of a P type;
the source end of the MOSFET is used as an input end, the drain end is used as an output end, and the gate end is used as a control end.
9. The protection circuit of a double-transistor forward converter circuit according to claim 1,
the upper power switch tube (Q1) and the lower power switch tube (Q2) are IGBT.
10. The protection circuit of a double-transistor forward converter circuit according to claim 1,
the set voltage is 0.2V, 0.5V, or 1V;
the current detection device (S1) is used for sampling the current flowing through the negative direct current bus or sampling the current flowing through the positive direct current bus;
the double-tube forward conversion circuit is a double-tube forward conversion circuit of the inverter welding machine.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201922122848.2U CN211046467U (en) | 2019-12-02 | 2019-12-02 | Protection circuit of double-tube forward conversion circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201922122848.2U CN211046467U (en) | 2019-12-02 | 2019-12-02 | Protection circuit of double-tube forward conversion circuit |
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| Publication Number | Publication Date |
|---|---|
| CN211046467U true CN211046467U (en) | 2020-07-17 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201922122848.2U Active CN211046467U (en) | 2019-12-02 | 2019-12-02 | Protection circuit of double-tube forward conversion circuit |
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| Country | Link |
|---|---|
| CN (1) | CN211046467U (en) |
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2019
- 2019-12-02 CN CN201922122848.2U patent/CN211046467U/en active Active
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