Circuit for carrying out short circuit detection by using anti-reverse field effect transistor

Abstract

According to the circuit for performing short circuit detection by using the anti-reverse field effect transistor, a first conduction end and a second conduction end of the anti-reverse field effect transistor are respectively connected with a voltage input end Vin and a voltage output end Vo, and the conduction direction of a parasitic diode of the anti-reverse field effect transistor is from the first conduction end to the second conduction end of the anti-reverse field effect transistor. The circuit for performing short circuit detection by using the anti-reverse field effect transistor comprises a voltage division circuit, a switching circuit and a switching tube Q3. The first end and the second end of the voltage division circuit are connected with the Vin and the first end of the switching circuit respectively, and the output end of the voltage division circuit is connected with the controlled end of the switching tube Q3. The first conduction end of the switch tube Q3 is connected with the first end of the voltage division circuit and the first conduction end of the anti-reverse field effect transistor, and the second conduction end of the switch tube Q3 is connected with the controlled end of the anti-reverse field effect transistor. The second end of the switching circuit is grounded, and when the switching circuit is switched on, the switching tube Q3 is switched on, so that the anti-reverse field effect transistor is switched off. According to the utility model, the fault from the load short circuit to the power supply in the anti-reverse circuit can be conveniently detected, and the loss is low.

Description

TECHNICAL FIELD

[0001] The utility model relates to protection circuit technology. BACKGROUND

[0002] Figure 1 And Figure 2 Respectively show the circuit principle drawing of the anti-reverse circuit of the existing diode D1 and the anti-reverse field effect tube Q1. In the circuit, if the positive pole of load 1 is directly short-circuited to the power supply (namely, short-circuited to the voltage input terminal Vin connected with the positive pole of the power supply, such as Figure 1 And Figure 2 The dotted line shown in the figure), it will bring the security risk. For example, the positive pole of the suspension damper solenoid valve of the car in running is directly short-circuited to the positive pole of the power supply, and the uncertain current path will bring greater security risk. Therefore, from the safety point of view, it is necessary to identify the situation that the positive pole of the load is short-circuited to the power supply, although the detection frequency is not high, but it needs to be detected.

[0003] When load 1 works, a current will flow, and when the current flowing through current detection resistor Rs1 and the current flowing through current detection resistor Rs2 has a large difference, the above short circuit can be identified. In addition, the short circuit can also be identified by detecting the voltage of Vin_CP point and comparing it with the voltage of the voltage output terminal Vo.

[0004] For the anti-reverse circuit using the anti-reverse field effect tube Q1, because the on-voltage drop of the anti-reverse field effect tube Q1 is very low, if the load 1 is directly short-circuited to the power supply, the current may still flow through the current detection resistor Rs1, and thus the short circuit cannot be successfully identified. When the diode D1 is used for anti-reverse, because the on-voltage drop of the diode D1 is usually large, when the load 1 is directly short-circuited to the power supply, the current will not flow through the current detection resistor Rs1 or only a small part of the current will pass through the current detection resistor Rs1, at this time, the short circuit can be well identified.

[0005] For the way of identifying the short circuit by comparing the voltage of Vin_CP point with the voltage of the voltage output terminal Vo, the diode anti-reverse is also easier to identify the situation that the load is short-circuited to the power supply. Moreover, in the case that the current flowing through is small, the anti-reverse circuit using the diode anti-reverse is easier to identify the short circuit.

[0006] However, the diode has a large voltage drop, and when a large current passes through, the loss is large. In addition, when there is a bulk current injection (BCI), if the subsequent load 1 does not work, the diode D1 will interfere with the voltage rectification into the node Vin_CP, which may cause the withstand voltage of the boost driving circuit 2 (in a specific application, the boost driving circuit 2 uses a charge pump IC) to be exceeded and damaged. If a reverse prevention field effect tube is used to prevent reverse, the channel current is bidirectional, and the interference voltage can be discharged to the power supply, so there is no risk as described above. SUMMARY

[0007] The technical problem to be solved by the utility model is to provide a circuit for short circuit detection using a reverse prevention field effect tube, which facilitates detection of a fault of short circuit of a load to a power supply in a reverse prevention circuit and has low loss.

[0008] The utility model discloses an utilize reverse prevention field effect tube to carry out short circuit detection's circuit, the first conduction end of reverse prevention field effect tube is connected with voltage input terminal Vin, the second conduction end of reverse prevention field effect tube is connected with voltage output terminal Vo, the conduction direction of the parasitic diode of reverse prevention field effect tube is from the first conduction end of reverse prevention field effect tube to the second conduction end of reverse prevention field effect tube, voltage output terminal Vo is connected with the first end of load, and the second end of load is grounded, and the circuit for short circuit detection using a reverse prevention field effect tube includes voltage dividing circuit, switching circuit and switch tube Q3, the first end of voltage dividing circuit is connected with voltage input terminal Vin, the second end of voltage dividing circuit is connected with the first end of switching circuit, and the output end of voltage dividing circuit is connected with the controlled end of switch tube Q3, the first conduction end of switch tube Q3 is connected with the first end of voltage dividing circuit and the first conduction end of reverse prevention field effect tube respectively, the second conduction end of switch tube Q3 is connected with the controlled end of reverse prevention field effect tube, the second end of switching circuit is grounded, and the controlled end of switching circuit is used for receiving control signal to be turned on or be turned off, when switching circuit is turned on, switch tube Q3 is turned on to make reverse prevention field effect tube be turned off, and when switching circuit is turned off, switch tube Q3 is turned off.

[0009] Further, the circuit for short circuit detection using a reverse prevention field effect tube includes current detection resistance Rs1 and current detection resistance Rs2, the current detection resistance Rs1 is connected in series between the second conduction end of the reverse prevention field effect tube and the voltage output terminal Vo, and the current detection resistance Rs2 is connected in series between the voltage output terminal Vo and the load or between the load and the ground.

[0010] The utility model has at least the following advantages and characteristics:

[0011] 1. The circuit of the embodiment of the present application maintains the channel conduction of the anti-field effect tube when not performing load short circuit detection, and when used for load short circuit detection, the channel of the anti-field effect tube is pulled off to switch to a parasitic diode conduction mode. The large conduction voltage drop characteristic of the parasitic diode facilitates the detection of the load-to-power positive short circuit fault. The present application takes into account the advantages of low anti-field loss of MOS tube and easy detection of load short circuit to power fault by using diode anti-field.

[0012] 2. The short circuit detection circuit using the anti-field effect tube of the embodiment of the present application is composed of discrete devices, has fewer devices and low cost. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 A circuit diagram of an existing anti-field circuit using a diode is shown.

[0014] Figure 2 A circuit diagram of an existing anti-field circuit using an anti-field effect tube is shown.

[0015] Figure 3 A circuit diagram of a short circuit detection circuit using an anti-field effect tube according to the first embodiment of the present application is shown.

[0016] Figure 4 A circuit diagram of a short circuit detection circuit using an anti-field effect tube according to the second embodiment of the present application is shown. DETAILED DESCRIPTION

[0017] The present application will be described in detail below with reference to the drawings and specific embodiments.

[0018] Figure 3 A circuit diagram of a short circuit detection circuit using an anti-field effect tube according to the first embodiment of the present application is shown. Please refer to Figure 3 The first conduction end of the anti-field effect tube Q1 is connected with the voltage input end Vin, the second conduction end of the anti-field effect tube Q1 is connected with the voltage output end Vo, and the conduction direction of the parasitic diode of the anti-field effect tube Q1 is from the first conduction end of the anti-field effect tube Q1 to the second conduction end of the anti-field effect tube Q1 (i.e. the direction of current flowing from the voltage input end Vin to the voltage output end Vo); the voltage output end Vo is connected with the first end of the load 1, and the second end of the load 1 is grounded. The load 1 can be a pure load or can contain its driving control circuit, such as high-side switch, H-bridge, low-side switch, etc. In actual work, the voltage input end Vin is connected with the positive pole of the power supply, Figure 3 GND in the above formula represents the power supply ground.

[0019] The circuit for short circuit detection using the anti-field effect tube in the embodiment comprises a voltage dividing circuit 3, a switch circuit 4 and a switch tube Q3.

[0020] The first end of the voltage dividing circuit 3 is connected with the voltage input end Vin, the second end of the voltage dividing circuit 3 is connected with the first end of the switch circuit 4, and the output end of the voltage dividing circuit 3 is connected with the controlled end of the switch tube Q3. In the embodiment, the voltage dividing circuit 3 comprises a resistor R3 and a resistor R4, and the resistor R3 is connected with the resistor R4 in series; the first end of the resistor R3 constitutes the first end of the voltage dividing circuit 3, the first end of the resistor R4 constitutes the second end of the voltage dividing circuit 3, and the common connection point of the second end of the resistor R3 and the second end of the resistor R4 constitutes the output end of the voltage dividing circuit 3.

[0021] The first conducting end of the switch tube Q3 is connected with the first end of the voltage dividing circuit 3 and the first conducting end of the anti-field effect tube Q1 respectively, and the second conducting end of the switch tube Q3 is connected with the controlled end of the anti-field effect tube Q1. In the embodiment, the switch tube Q3 is a PNP triode, and the controlled end, the first conducting end and the second conducting end of the switch tube Q3 are the base, the emitter and the collector of the PNP triode respectively. The resistor R3 functions as a bias discharge resistor of the PNP triode Q3. Further, the circuit for short circuit detection using the anti-field effect tube in the embodiment further comprises a resistor R2, and the two ends of the resistor R2 as the bias discharge resistor are connected with the first conducting end and the second conducting end of the switch tube Q3 respectively.

[0022] The second end of the switch circuit 4 is grounded, and the controlled end of the switch circuit 4 is used for receiving a control signal to turn on or turn off; when the switch circuit 4 is turned on, the switch tube Q3 is turned on to turn off the anti-field effect tube Q1, and when the switch circuit 4 is turned off, the switch tube Q3 is turned off.

[0023] In the embodiment, the switch circuit 4 comprises an NPN triode Q4, a resistor R5 and a resistor R6, and the resistor R5 and the resistor R6 function as a current limiting resistor and a bias discharge resistor respectively. The first end of the resistor R5 constitutes the controlled end of the switch circuit 4, the collector of the NPN triode Q4 constitutes the first end of the switch circuit 4, the common connection point of the emitter of the NPN triode Q4 and the first end of the resistor R6 constitutes the second end of the switch circuit 4, and the base of the NPN triode Q4 is connected with the second end of the resistor R5 and the second end of the resistor R6 respectively. In a specific application, the controlled end of the switch circuit 4 is connected with a general input and output port MCU_GPIO of a single-chip microcomputer to receive a control signal sent by the single-chip microcomputer.

[0024] In the first embodiment, the second conduction end of the anti-field effect tube Q1 is connected with the first conduction end of the high-side switch Q2, and the second conduction end of the high-side switch Q2 is connected with the voltage output end Vo (in other embodiments, the high-side switch Q2 can also not be arranged). The current detection resistor Rs1 is connected in series between the second conduction end of the anti-field effect tube Q1 and the first conduction end of the high-side switch Q2, and the current detection resistor Rs2 is connected in series between the voltage output end Vo and the load 1 (the current detection resistor Rs2 can also be connected in series between the load 1 and the ground). The anti-field effect tube Q1 is an NMOS tube, and the controlled end, the first conduction end and the second conduction end of the anti-field effect tube Q1 are the gate, the source and the drain of the NMOS tube Q1 respectively. The high-side switch Q2 is an NMOS tube, and the controlled end, the first conduction end and the second conduction end of the high-side switch Q2 are the gate, the drain and the source of the NMOS tube Q2 respectively. The controlled end of the anti-field effect tube Q1 is connected with the first output end of the boost driving circuit 2 through the driving resistor R1, the second output end of the boost driving circuit 2 is connected with the controlled end of the high-side switch Q2 through the driving resistor R7, and the voltage input end of the boost driving circuit 2 is connected with the second conduction end of the anti-field effect tube Q1 (that is, connected with the Vin_CP point, as the power supply point of the boost driving circuit 2). Figures 1 to 4 The Vdri in the formula (1) and the Vdri in the formula (2) all represent the driving voltage output by the boost driving circuit 2 to the high-side switch Q2. In a specific embodiment, the boost driving circuit 2 adopts a charge pump IC, for example, a charge pump integrated in a power management chip with a model number of TLE9461. In other embodiments, the charge pump IC can also be integrated into other integrated circuits.

[0025] The working principle of the circuit for short circuit detection by using the anti-field effect tube according to an embodiment of the utility model is described as follows.

[0026] When the detection of the short circuit of the load 1 to the positive electrode of the power supply is not performed, the single-chip microcomputer outputs a low-level signal to the controlled end of the switching circuit 4, the NPN triode Q4 is not conductive, the PNP triode Q3 is off, and the channel of the anti-field effect tube Q1 is conductive, which works in a low conduction voltage drop and a low loss state.

[0027] When the detection of the short circuit of the load 1 to the positive electrode of the power supply is needed to be performed, the single-chip microcomputer outputs a high-level signal to the controlled end of the switching circuit 4, the NPN triode Q4 is conductive, the second end of the voltage dividing circuit 3 is pulled to the ground, and the PNP triode Q3 is conductive, the Vgs of the anti-field effect tube Q1 is clamped off by the PNP triode Q3, the channel of the anti-field effect tube Q1 is off, and the parasitic diode of the anti-field effect tube Q1 is conductive. The conduction characteristic of the parasitic diode of the MOSFET is generally poor, and the conduction voltage drop is relatively large, so that the short circuit fault of the load to the positive electrode of the power supply can be easily detected.

[0028] After the short circuit detection is completed, the single-chip microcomputer outputs a low-level signal to the controlled end of the switching circuit 4, thereby maintaining the low on-voltage drop and low loss state of the channel of the anti-back field effect tube Q1.

[0029] Figure 4 The circuit diagram of the circuit for short circuit detection by using the anti-back field effect tube according to the second embodiment of the utility model is shown, please refer to Figure 4 The main difference between the second embodiment and the first embodiment is that the anti-back field effect tube Q1 uses a PMOS tube, the controlled end, the first conducting end and the second conducting end of the anti-back field effect tube are the gate, the drain and the source of the PMOS tube Q1 respectively, and the controlled end of the anti-back field effect tube Q1 is connected to the ground through the driving resistor R1.

[0030] The controlled end of the high-side switch Q2 is connected to the output end of the boost driving circuit 2 through the driving resistor R7, and the voltage input end of the boost driving circuit 2 is connected to the second conducting end of the anti-back field effect tube Q1.

[0031] The advantage of using the PMOS tube for the anti-back field effect tube Q1 is that when there is a large current injection (i.e. BCI) when the charge pump IC is in sleep mode, the channel of the PMOS tube is still in the conducting state, and the voltage can be backfilled to the power supply, so that the potential of the Vin_CP point will not be raised.

[0032] The utility model maintains the channel conduction of the anti-back field effect tube when not performing load short circuit detection, and when used for load short circuit detection, the channel of the anti-back field effect tube is pulled off, so that it is switched to the parasitic diode conduction mode, and the large conduction voltage drop characteristic of the parasitic diode is used, thereby facilitating the detection of the load-to-positive electrode short circuit fault of the power supply.

[0033] Obviously, those skilled in the art can make various modifications and variations to the utility model without departing from the spirit and scope of the utility model. Thus, if these modifications and variations of the utility model fall within the scope of the claims of the utility model and the equivalent technologies thereof, the utility model also intends to include these modifications and variations.

Claims

1. A circuit for short circuit detection using a field crowbar effect tube, a first conducting terminal of the field crowbar effect tube being connected to a voltage input terminal Vin, a second conducting terminal of the field crowbar effect tube being connected to a voltage output terminal Vo, a conducting direction of a parasitic diode of the field crowbar effect tube being from the first conducting terminal of the field crowbar effect tube to the second conducting terminal of the field crowbar effect tube; the voltage output terminal Vo being connected to a first terminal of a load, a second terminal of the load being grounded, characterized in that, The circuit for short circuit detection by using the anti-field effect tube comprises a voltage dividing circuit, a switch circuit and a switch tube Q3. The first end of the voltage dividing circuit is connected with a voltage input terminal Vin, the second end of the voltage dividing circuit is connected with the first end of the switch circuit, and the output terminal of the voltage dividing circuit is connected with the controlled terminal of the switch tube Q3. The first conducting terminal of the switch tube Q3 is connected with the first end of the voltage dividing circuit and the first conducting terminal of the anti-field effect tube respectively, and the second conducting terminal of the switch tube Q3 is connected with the controlled terminal of the anti-field effect tube. The second end of the switch circuit is grounded, and the controlled terminal of the switch circuit is used for receiving a control signal to be turned on or turned off. When the switch circuit is turned on, the switch tube Q3 is turned on to make the anti-field effect tube turned off, and when the switch circuit is turned off, the switch tube Q3 is turned off.

2. The circuit for short detection using the anti-field proof effect tube according to claim 1, wherein The switch circuit comprises an NPN triode Q4, a resistor R5 and a resistor R6; the first end of the resistor R5 constitutes the controlled terminal of the switch circuit, the collector of the NPN triode Q4 constitutes the first end of the switch circuit, the common connection point of the emitter of the NPN triode Q4 and the first end of the resistor R6 constitutes the second end of the switch circuit, and the base of the NPN triode Q4 is connected with the second end of the resistor R5 and the second end of the resistor R6 respectively.

3. The circuit for short detection using anti-field effect tube according to claim 1, wherein The switch tube Q3 is a PNP triode, and the controlled terminal, the first conducting terminal and the second conducting terminal of the switch tube Q3 are the base, the emitter and the collector of the PNP triode respectively.

4. The circuit for short detection using the anti-field effect tube according to claim 1 or 3, wherein The circuit for short circuit detection by using the anti-field effect tube comprises a resistor R2, and the two ends of the resistor R2 are connected with the first conducting terminal and the second conducting terminal of the switch tube Q3 respectively.

5. The circuit for short detection using anti-field effect tube according to claim 1, wherein The voltage dividing circuit comprises a resistor R3 and a resistor R4, and the resistor R3 is connected with the resistor R4 in series; the first end of the resistor R3 constitutes the first end of the voltage dividing circuit, the first end of the resistor R4 constitutes the second end of the voltage dividing circuit, and the common connection point of the second end of the resistor R3 and the second end of the resistor R4 constitutes the output terminal of the voltage dividing circuit.

6. The circuit for short detection using anti-field proof effect tube according to claim 1, wherein The circuit for short circuit detection by using the anti-field effect tube comprises a current detection resistor Rs1 and a current detection resistor Rs2. The current detection resistor Rs1 is connected in series between the second conducting terminal of the anti-field effect tube and a voltage output terminal Vo, and the current detection resistor Rs2 is connected in series between the voltage output terminal Vo and the load or between the load and the ground.

7. The circuit for short detection using anti-field effect tube according to claim 1, wherein The anti-field effect tube is an NMOS tube, and the controlled terminal, the first conducting terminal and the second conducting terminal of the anti-field effect tube are the gate, the source and the drain of the NMOS tube respectively.

8. The circuit for short detection using anti-field effect tube according to claim 7, wherein The second conducting terminal of the anti-field effect tube is connected with the first conducting terminal of a high-side switch, and the second conducting terminal of the high-side switch is connected with a voltage output terminal Vo. The controlled terminal of the anti-field effect tube is connected with the first output terminal of a boost driving circuit through a driving resistor R1, the second output terminal of the boost driving circuit is connected with the controlled terminal of the high-side switch through a driving resistor R7, and the voltage input terminal of the boost driving circuit is connected with the second conducting terminal of the anti-field effect tube.

9. The circuit for short detection using anti-field effect tube according to claim 1, wherein The anti-inverse field effect tube is a PMOS tube, and the controlled end, the first conducting end and the second conducting end of the anti-inverse field effect tube are the gate, the drain and the source of the PMOS tube respectively; the controlled end of the PMOS tube is connected to the ground through a driving resistor R1.

10. The circuit for short detection using the anti-field effect tube according to claim 9, wherein The second conducting end of the anti-inverse field effect tube is connected to the first conducting end of the high-side switch, the second conducting end of the high-side switch is connected to the voltage output end Vo, the controlled end of the high-side switch is connected to the output end of the boost driving circuit through a driving resistor R7, and the voltage input end of the boost driving circuit is connected to the second conducting end of the anti-inverse field effect tube.

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