CN213693143U - Temperature compensation short-circuit protection circuit of power solid-state switch - Google Patents
Temperature compensation short-circuit protection circuit of power solid-state switch Download PDFInfo
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- CN213693143U CN213693143U CN202022587477.8U CN202022587477U CN213693143U CN 213693143 U CN213693143 U CN 213693143U CN 202022587477 U CN202022587477 U CN 202022587477U CN 213693143 U CN213693143 U CN 213693143U
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Abstract
A temperature compensation short circuit protection circuit of a power solid-state switch comprises at least one power switch, a comparator and at least one temperature coefficient resistor, wherein a control end of the power switch is controlled by a control signal to enable the power switch to be switched on or switched off; the first comparison end of the comparator is coupled to an electric output end of the power switch through a first diode, the second comparison end of the comparator is connected with a comparison potential, the power switch is controlled to be turned off when the first comparison end is higher than the comparison potential, the comparison potential is a reference point voltage generated by voltage division of the temperature coefficient resistor, the temperature coefficient resistor is attached to a shell of the power switch, the resistance value of the temperature coefficient resistor can change along with the temperature of the power switch, the time for starting the protection signal also changes along with the change, and the protection effect of controlling the temperature compensation of the power switch is achieved.
Description
Technical Field
The utility model relates to a temperature compensation short circuit protection circuit of a power solid-state switch; more particularly, to a power protection circuit using a power solid state switch as a switching circuit for switching on and off a current, especially a protection circuit for a high current power device.
Background
As shown in fig. 1, a conventional power solid-state switch short-circuit protection circuit is disclosed, which includes one or more parallel power solid-state switches Q1, and a protection circuit composed of multiple resistors, capacitors C1-C3, a comparator U3, and diodes D1-D3. The short-circuit protection circuit operates on the principle that when the power solid-state switch Q1 is short-circuited, the voltage across the source and drain of the power solid-state switch Q1 is raised.
When the voltage across the power solid-state switch Q1 plus the voltage across the diode D1, i.e., the voltage at the fourth pin of the comparator U3 is higher than the voltage at the third pin (+) of the comparator U3, the first pin output of the comparator U3 is low, and the gate of the power solid-state switch Q1 is pulled low through the diode D3, so that the power solid-state switch Q1 is turned off.
The resistor R7 and the capacitor C3 connected to the first pin of the comparator U3 can ensure that the short-circuit protection signal is maintained for a period of time to ensure that the power solid-state switch Q1 has enough time to reduce the temperature of the main body when a short circuit occurs, thereby preventing the power solid-state switch Q1 from being heated and not being dissipated due to intermittent short circuit, and preventing the temperature from continuously rising and finally being burned.
However, the short-circuit protection circuit for the power solid-state switch has the disadvantage that when the temperature of the main body of the power solid-state switch Q1 changes, the on-resistance value changes due to the resistance temperature coefficient thereof, and further the current value triggering the short-circuit protection is affected, and when the current is too large, the internal damage of the main body of the power solid-state switch may be caused, and the service life of the product may be reduced.
SUMMERY OF THE UTILITY MODEL
Therefore, the utility model discloses a main objective designs a compensation mode promptly, lets power solid state switch be less than under the work limiting temperature, along with power solid state switch on resistance value's change, the compensation can all be done to the short-circuit protection circuit for the current value that triggers short-circuit protection can be maintained in a small error range, reaches the efficiency of protection power solid state switch extension product life.
To achieve the above objective, the present invention provides a temperature compensation short-circuit protection circuit for a power solid-state switch, which includes at least one power switch, a comparator and at least one temperature coefficient resistor, wherein a control terminal (gate terminal) of the power switch is controlled by a control signal to turn on or off the power switch; the first comparison end (-) of the comparator is coupled to an electric output end of the power switch through a first diode, the second comparison end (+) of the comparator is connected with a comparison potential, when the first comparison end potential is higher than the comparison potential, the power switch is controlled to be cut off, the comparison potential is a reference point voltage generated by dividing the voltage of the temperature coefficient resistor, the temperature coefficient resistor is attached to a shell of the power switch, the resistance value of the temperature coefficient resistor can change along with the temperature of the power switch, the time for starting the protection signal also changes along with the change, and the protection effect of controlling the temperature compensation of the power switch is achieved.
The utility model provides a temperature compensation short-circuit protection circuit of power solid state switch, it includes:
at least one power switch, which has a control end, an electric output end and a grounding end, wherein the control end is controlled by a control signal to make the power switch turn on or off;
a comparator having a first comparing terminal, a second comparing terminal and an output terminal, wherein the first comparing terminal is coupled to the power output terminal through a first diode, the second comparing terminal is connected to a comparing potential, and the output terminal is coupled to the control terminal through a second diode; when the power switch is short-circuited, comparing the potential of the first comparison end with the comparison potential to enable the output end to output a protection signal to control the power switch to be cut off; and
at least one temperature coefficient resistor attached to the shell of the power switch and coupled to the second comparison end to generate the comparison potential; the resistance value of the temperature coefficient resistor changes along with the temperature of the power switch, the comparison potential also changes along with the change, and further the generation time of the protection signal also changes along with the change, thereby achieving the protection effect of controlling the temperature compensation of the power switch.
In one embodiment of the present invention, the power switch is a MOSFET, the control terminal is a gate terminal, the power output terminal is a drain terminal, and the ground terminal is a source terminal.
In an embodiment of the present invention, the first comparing terminal of the comparator is a-terminal and the second comparing terminal is a + terminal, when the first comparing terminal is higher than the comparing potential of the second comparing terminal, the protection signal outputted by the output terminal is a low potential, and when the first comparing terminal is lower than the comparing potential of the second comparing terminal, the protection signal outputted by the output terminal is a high potential.
In an embodiment of the present invention, the first comparing terminal is further coupled to the control terminal through a third diode, when the control signal is at a low potential, the potential of the first comparing terminal is changed to about 0.7V due to the conduction of the third diode, and is lower than the potentials of the two comparing terminals, so that the protection signal is maintained at the low potential, and the short circuit protection is not activated.
In an embodiment of the present invention, the temperature coefficient resistor is further connected to the second comparison terminal after being connected in series with a first resistor, so that the generated comparison potential can be changed within a temperature range of the power switch, thereby ensuring that the short-circuit protection current value triggering the power switch is not too large.
In an embodiment of the present invention, the temperature coefficient resistor is connected in series with the first resistor and then connected in parallel with a first capacitor for filtering noise on the second comparing end of the comparator, so that the comparing potential is not fluctuated by noise images.
In an embodiment of the present invention, the two ends of the third diode are further connected to a second resistor and a third resistor respectively connected to a second capacitor in series to the ground terminal to form a delay circuit, when the power switch is not short-circuited, the protection signal is at a low potential, the output high potential of the comparator charges the second capacitor through the second resistor, when the short-circuited occurs, the protection signal is at a high potential, the second capacitor is delayed by discharging through the third resistor, and the power switch is maintained at a cut-off time, so that the power switch has a sufficient time to cool down.
In an embodiment of the present invention, the first comparing terminal of the comparator is further connected to a third capacitor connected in parallel to a fourth resistor, the third capacitor prevents malfunction of short-circuit protection due to noise when the power switch is turned on by filtering, because of inductive noise generated between the circuit and the device, and when the short-circuit state is released, the charge on the third capacitor is released through the fourth resistor.
In an embodiment of the present invention, when the power switch is short-circuited, the voltage of the power output terminal is raised, so that the voltage of the first comparing terminal is the voltage of the power switch plus the voltage of the first diode, which is higher than the comparing potential, the comparator outputs a low potential, the potential of the control terminal is pulled down via the third diode, so that the protection signal is activated, and the power switch is turned off.
Drawings
Fig. 1 is a diagram of a conventional power solid-state switch short-circuit protection circuit.
Fig. 2 is a schematic diagram of the temperature compensated short-circuit protection circuit of the solid-state power switch of the present invention.
Description of reference numerals: 11-power switch (Q1); 111-a control terminal; 112-a power output; 113-ground; 12-a comparator (U3); 121 — a first comparison terminal (-); 122-second comparison terminal (+); 123-an output end; 13-temperature coefficient resistance (RT 1); 14-a control signal; 15-a first diode (D1); 16-a second diode (D3); 17-a third diode (D2); 18-a guard signal; 19-a first resistance (R4); 20-resistance (R3); 21-a first capacitance (C2); 22-second resistance (R7); 23-third resistance (R6); 24-a second capacitance (C3); 25-third capacitance (C1); 26-fourth resistance (R2).
Detailed Description
Please refer to fig. 2, which is a diagram of a temperature compensation short-circuit protection circuit of the present invention, the temperature compensation short-circuit protection circuit of a power solid-state switch of the present invention includes at least one power switch (Q1)11, a comparator (U3)12 and at least one temperature coefficient resistor (RT1)13, wherein the power switch (Q1)11 has a control terminal 111, an electric power output terminal 112 and a grounding terminal 113, and the control terminal 111 of the power switch (Q1)11 is controlled by a control signal 14 to turn on or off the power switch (Q1) 11. Preferably, the power switch 11 is a MOSFET, the control terminal 111 is a gate terminal, the power output terminal 112 is a drain terminal, and the ground terminal 113 is connected to a source terminal.
Wherein the comparator (U3)12 has a first comparing terminal 121, a second comparing terminal 122 and an output terminal 123, in the embodiment of the present invention, the first comparing terminal of the comparator (U3)12 is (-) terminal, and the second comparing terminal is (+) terminal. The first comparing terminal (-)121 of the comparator (U3)12 is connected to a first diode (D1)15, which is further connected to the power output terminal 112 of the power switch (Q1)11, and the second comparing terminal 122 of the comparator (U3)12 is connected to a comparing potential, and the comparing potential is obtained by serially dividing the voltage of the temperature coefficient resistor (RT1)13 and other resistors (R4, R3), and is a reference voltage for starting short circuit protection.
The output terminal 123 of the comparator (U3)12 is connected to a second diode (D3)16 and then connected to the control terminal 111 of the power switch (Q1), the first comparison terminal 121 is further coupled to the control terminal through a third diode (D2)17, when the control signal 14 is at a low potential, the potential of the first comparison terminal 121 is about 0.7V due to the conduction of the third diode (D2)17, which is lower than the comparison potential of the second comparison terminal 122, so that the output terminal 123 of the comparator (U3)12 outputs a protection signal 18 at a low potential, and short-circuit protection is not enabled until the control terminal 111 of the power switch (Q1) 11.
When the power switch (Q1)11 is shorted, the voltage across the power switch (Q1)11 is raised, the voltage of the first comparing terminal (-)121 of the comparator (U3) is the voltage of the power switch (Q1)11 plus the voltage of the first diode (D1)15, so that the voltage of the first comparing terminal (-)121 is higher than the comparing voltage of the second comparing terminal (+)122, the output terminal 123 of the comparator (U3)12 outputs a protection signal 18 with a low voltage, and the voltage of the control terminal 111 of the power switch (Q1)11 is pulled down by the third diode (D2)17, so that the control power switch (Q1)11 is turned off.
The utility model discloses utilize temperature coefficient resistance (RT1)13 to attach on power switch (Q1) 11's casing, this temperature coefficient resistance (RT1)13 connects in series a first resistance (R4)19 and connects in the second comparison end 122 of this comparator (U3)12, a resistance (R3)20 to Vcc power end is connected again, so this comparison potential is the partial pressure that temperature coefficient resistance (RT1)13 connects in series first resistance (R4)19 and obtains, this temperature coefficient resistance (RT1)13 and this first resistance (R4)19 connect in series after more parallelly connected a first electric capacity (C2)21, be used for the noise on filtering comparator (U3)12 second comparison end 122, make this comparison potential not receive the noise image and fluctuate uncertain.
Wherein two ends of the third diode (D2)17 are further respectively connected to a second resistor (R7)22 and a third resistor (R6)23 connected in series with a second capacitor (C3)24 to the ground 113 to form a delay loop, when the power switch (Q1)11 is not short-circuited, the output terminal 123 of the comparator (U3)12 outputs a high voltage potential to charge the second capacitor (C3)24 through the second resistor (R7) 22; when a short circuit occurs, the output terminal 123 of the comparator (U3)12 outputs a low voltage, the second capacitor (C3)24 discharges through the third resistor (R6)23 for a delay time, and the power switch (Q1)11 is kept turned off for a period of time, so that it has a sufficient time to cool down.
Since the resistance of the temperature coefficient resistor (RT1)13 will change with the temperature of the power switch (Q1)11, a positive temperature coefficient resistor (PTC) is used in the embodiment of the present invention, i.e. the resistance will become larger with the temperature rise, and a negative temperature coefficient resistor (NTC) can be used in other embodiments. Therefore, when the temperature of the power switch (Q1)11 increases, the resistance of the temperature coefficient resistor (RT1)13 also increases, the comparison potential increases with the increase of the divided voltage, the time for the output terminal 123 of the comparator (U3)12 to generate the low potential protection signal 18 also increases, so the time for the power switch (Q1)11 to turn off is also increased, the temperature of the power switch (Q1)11 starts to decrease, the comparison potential also decreases with the temperature, and the protection effect of controlling the temperature compensation of the power switch (Q1)11 can be achieved.
The first comparing end 121 of the comparator (U3)12 is further connected to a third capacitor (C1)25 connected in parallel to a fourth resistor (R2)26, and the third capacitor (C1)25 functions to filter out inductive noise generated between circuits or components at the turn-on moment of the power switch (Q1)11, thereby preventing malfunction of short-circuit protection caused by noise. When a short circuit occurs, the voltage across the channel of the power switch (Q1)11 is raised, and the effect of the fourth resistor (R2)26 is negligible because the on-resistance of the power switch (Q1)11 is much lower than that of the fourth resistor (R2); when the short circuit state is released, the charge on the third capacitor (C1)25 is released through the fourth resistor (R2) 26.
To sum up, the utility model discloses an advantage can accelerate power solid state switch (Q1)11 short-circuit protection circuit's reaction, reduces the probability of short-circuit protection circuit failure, avoids before short-circuit protection circuit actuates, triggers the short-circuit protection of power end in advance, promotes the reliability and the robustness of product.
Claims (9)
1. A temperature compensated short circuit protection circuit for a power solid state switch, comprising:
at least one power switch, which has a control end, an electric output end and a grounding end, wherein the control end is controlled by a control signal to make the power switch turn on or off;
a comparator having a first comparing terminal, a second comparing terminal and an output terminal, wherein the first comparing terminal is coupled to the power output terminal through a first diode, the second comparing terminal is connected to a comparing potential, and the output terminal is coupled to the control terminal through a second diode; when the power switch is short-circuited, comparing the potential of the first comparison end with the comparison potential to enable the output end to output a protection signal to control the power switch to be cut off; and
at least one temperature coefficient resistor attached to the shell of the power switch and coupled to the second comparison end to generate the comparison potential; the resistance value of the temperature coefficient resistor changes along with the temperature of the power switch, the comparison potential also changes along with the change, and further the generation time of the protection signal also changes along with the change, thereby achieving the protection effect of controlling the temperature compensation of the power switch.
2. The temperature-compensated short-circuit protection circuit of claim 1, wherein the power switch is a MOSFET, the control terminal is a gate terminal, the power output terminal is a drain terminal, and the ground terminal is a source terminal.
3. The temperature-compensated short-circuit protection circuit of claim 1, wherein the first comparing terminal of the comparator is a negative terminal and the second comparing terminal is a positive terminal, when the first comparing terminal is higher than the comparing potential of the second comparing terminal, the protection signal outputted from the output terminal is a low potential, and when the first comparing terminal is lower than the comparing potential of the second comparing terminal, the protection signal outputted from the output terminal is a high potential.
4. The temperature-compensated short-circuit protection circuit of claim 3, wherein the first comparing terminal is further coupled to the control terminal through a third diode, and when the control signal is at a low voltage level, the voltage level of the first comparing terminal is about 0.7V due to the conduction of the third diode, which is lower than the voltage levels of the two comparing terminals, so that the protection signal is maintained at the low voltage level and short-circuit protection is not enabled.
5. The temperature-compensated short-circuit protection circuit of claim 1, wherein the temperature coefficient resistor is further connected to the second comparison terminal after being connected in series with a first resistor, so that the generated comparison potential can vary within a temperature range of the power switch, thereby ensuring that the short-circuit protection current value triggering the power switch is not too large.
6. The temperature-compensated short-circuit protection circuit of claim 5, wherein the temperature coefficient resistor is connected in series with the first resistor and then connected in parallel with a first capacitor for filtering noise at the second comparing terminal of the comparator, so that the comparing potential is not fluctuated by noise image.
7. The temperature-compensated short-circuit protection circuit of claim 4, wherein two ends of the third diode are respectively connected to a second resistor and a third resistor connected in series with a second capacitor to the ground terminal to form a delay circuit, when the power switch is not short-circuited, the protection signal is at a low potential, the high potential output from the comparator charges the second capacitor through the second resistor, when the short-circuit occurs, the protection signal is at a high potential, the second capacitor is discharged through the third resistor for delay, and the power switch is kept off for a period of time, so that the power switch has a sufficient time to cool down.
8. The temperature-compensated short-circuit protection circuit of claim 4, wherein the first comparing terminal of the comparator is further connected to a third capacitor connected in parallel with a fourth resistor, the third capacitor is used to filter out inductive noise generated between circuits or components at the turn-on instant of the power switch, so as to prevent malfunction of short-circuit protection caused by noise, and when the short-circuit state is released, the charge on the third capacitor is released through the fourth resistor.
9. The temperature-compensated short-circuit protection circuit of claim 8, wherein when the power switch is short-circuited, the voltage at the power output terminal is raised, such that the voltage at the first comparing terminal is the voltage across the power switch plus the voltage across the first diode, which is higher than the comparing potential, the comparator outputs a low potential, the potential at the control terminal is pulled low via the third diode, such that the protection signal is enabled, and the power switch is disabled.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202022587477.8U CN213693143U (en) | 2020-11-10 | 2020-11-10 | Temperature compensation short-circuit protection circuit of power solid-state switch |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202022587477.8U CN213693143U (en) | 2020-11-10 | 2020-11-10 | Temperature compensation short-circuit protection circuit of power solid-state switch |
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| CN213693143U true CN213693143U (en) | 2021-07-13 |
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| CN202022587477.8U Active CN213693143U (en) | 2020-11-10 | 2020-11-10 | Temperature compensation short-circuit protection circuit of power solid-state switch |
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