CN216160775U

CN216160775U - Diagnostic circuit for power driving circuit

Info

Publication number: CN216160775U
Application number: CN202122098395.1U
Authority: CN
Inventors: 李貌; 马少军
Original assignee: Keboda Technology Co ltd
Current assignee: Keboda Technology Co ltd
Priority date: 2021-09-01
Filing date: 2021-09-01
Publication date: 2022-04-01
Anticipated expiration: 2031-09-01

Abstract

A diagnostic circuit for a power driver circuit includes a current sampling circuit, a current information processing circuit, and a comparison diagnostic circuit. The current sampling circuit is used for collecting the current I1 flowing from the positive pole of the power supply to the current inflow end of the power driving circuit and outputting a first voltage signal V_I1And collecting the current I2 flowing from the current outlet end of the power driving circuit to the negative pole of the power supply and outputting a second voltage signal V_I2. The current information processing circuit is used for processing the first voltage signal V_I1And a second voltage signal V_I2The voltage Vc is output after processing. The comparison diagnosis circuit is used for judging whether the voltage Vc is greater than the upper limit V of the voltage_TH1And whether it is less than the lower voltage limit V_TH2At Vc greater thanV_TH1And Vc is less than V_TH2First and second diagnostic signals are generated, respectively. The utility model can quickly detect the abnormity and respond when the output of the power driving circuit is abnormal.

Description

Diagnostic circuit for power driving circuit

Technical Field

The present invention relates to a protection technique for a power driver circuit.

Background

Power driving circuits are often used in electronic products, and the load of the power driving circuit may be a pure resistive load, an inductive load or a capacitive load. In practical applications or product functions, it is required that the product can be protected in abnormal load conditions, such as the output port of the power driving circuit is shorted to ground, shorted to a voltage source, or the output current is too large, and therefore, the power driving circuit is required to have a corresponding protection function design to detect these abnormal operating conditions and quickly respond to protection.

Disclosure of Invention

The present invention is directed to a diagnostic circuit for a power driving circuit, which can quickly detect and respond to an abnormal condition of an output of the power driving circuit, such as a short circuit or an open circuit at an output terminal of the driving circuit.

According to the diagnostic circuit of the power driving circuit provided by the embodiment of the utility model, the power driving circuit comprises a current inflow end, a current outflow end, a first output end and a second output end; the current inflow end and the current outflow end are respectively used for being connected to the positive pole and the negative pole of a power supply, and the first output end and the second output end are respectively used for being connected with the first end and the second end of a load; the diagnostic circuit includes: a current sampling circuit for collecting the current I1 flowing from the positive pole of the power supply into the current inflow end of the power driving circuit and outputting a first voltage signal V related to the current I1_I1And collecting the current I2 flowing from the current outlet end of the power driving circuit to the negative pole of the power supply and outputting a second voltage signal V related to the current I2_I2(ii) a The input end of the current information processing circuit is connected with the output end of the current sampling circuit and is used for processing the first voltage signal V_I1And a second voltage signal V_I2Processed to output voltage Vc, Vc ═ V_REF+(I1-I2)*A，V_REFIs a reference voltage, and A is a magnification factor; a comparison diagnosis circuit, the input end of which is connected with the output end of the current information processing circuit and used for judging whether the voltage Vc is larger than the preset upper voltage limit V_TH1And whether it is less than the preset lower voltage limit V_TH2At Vc greater than V_TH1Generating a first diagnostic signal when Vc is less than V_TH2A second diagnostic signal is generated.

The utility model has at least the following technical effects:

1. the diagnostic circuit of the embodiment of the utility model generates a first diagnostic signal when the high-end current I1 of the power driving circuit is far larger than the low-end current I2, and generates a second diagnostic signal when the low-end current I2 of the power driving circuit is far larger than the high-end current I1, thereby providing the abnormal detection that reliable load current flows to an error circuit network, the output end of the power driving circuit is short-circuited to a power supply, and the output end of the power driving circuit is short-circuited to the ground, and improving the reliability of the power driving circuit;

2. the diagnostic circuit of the embodiment of the utility model is easy to adjust the protection threshold value, thereby having good flexibility.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

Fig. 1 shows a circuit schematic of a diagnostic circuit of a power driver circuit according to an embodiment of the utility model.

Fig. 2 to 5 respectively exemplarily show schematic diagrams of four different types of power driving circuits to which the diagnostic circuit according to the embodiment of the present invention is applied.

Fig. 6 shows four abnormal conditions of the low-side switch driving circuit.

FIGS. 7 to 9 show the determination of the upper voltage limit V, respectively_TH1And lower voltage limit V_TH2The principle of (1).

Fig. 10 shows a circuit diagram of a first specific implementation of the diagnostic circuit of an embodiment of the present invention.

Fig. 11 shows a circuit diagram of a second specific implementation of the diagnostic circuit of an embodiment of the present invention.

Detailed Description

Fig. 1 shows a circuit schematic of a diagnostic circuit of a power driver circuit according to an embodiment of the utility model. The power driving circuit 100 includes a current input terminal a1, a current output terminal a2, a first output terminal O1, and a second output terminal O2; the current inflow terminal a1 and the current outflow terminal a2 are respectively connected to the positive pole and the negative pole of the power source Vin, and the first output terminal O1 and the second output terminal O2 are respectively connected to the first terminal and the second terminal of the load 200.

The diagnostic circuit includes a current sampling circuit, a current information processing circuit 2, and a comparison diagnostic circuit 3.

The current sampling circuit includes a high-side current sampling circuit 11 and a low-side current sampling circuit 12. The high-side current sampling circuit 11 is used for collecting a current I1 flowing from the positive pole of the power Vin into a current inflow end A1 of the power driving circuit and outputting a first voltage signal V related to the current I1_I1The low-side current sampling circuit 12 collects a current I2 returned from the current outlet A2 of the power driving circuit to the cathode of the power source Vin, and outputs a second voltage signal V related to the current I2_I2。

The input end of the current information processing circuit 2 is connected with the output end of the current sampling circuit and is used for processing the first voltage signal V_I1And a second voltage signal V_I2Processed to output voltage Vc, Vc ═ V_REF+(I1-I2)*A，V_REFFor reference voltage, a is the magnification factor.

The input end of the comparison diagnosis circuit 3 is connected with the output end of the current information processing circuit 2 and is used for judging whether the voltage Vc is larger than a preset upper voltage limit V_TH1And whether it is less than the preset lower voltage limit V_TH2At Vc greater than V_TH1And Vc is less than V_TH2A diagnostic signal is generated.

In fig. 1, the output drive current Iout of the power drive circuit 100 is output from the first output terminal O1, flows through the load 200, and then flows into the power drive circuit 100 from the second output terminal O2. The input current I1 of the power driving circuit 100 is supplied by the power Vin and flows into the power driving circuit 100 through the current inflow terminal a1, and the return current I2 of the power driving circuit 100 flows out through the current outflow terminal a2 and returns to the negative pole of the power Vin.

The power driving circuit 100 and the load 200 may have various forms, the power driving circuit 100 may be, for example, a high-side switch driving circuit, a low-side switch driving circuit, a full-bridge driving circuit, etc., and the load 200 may be a pure resistive load, an inductive load, or a capacitive load. The requirement for the current sampling circuit is that the full high side current from a0 to a1 and the low side current from a2 to the cathode of the source Vin can always be collected. According to the circuit configuration in fig. 1, according to the characteristics of the lumped circuit and kirchhoff's current law, it can be always obtained that the current flowing into the terminal a1 is equal to the current flowing out of the terminal a2, i.e., I1 is equal to I2.

In fig. 2, the power driving circuit 100 is a high-side switching driving circuit, and fig. 2 shows a switching device S1 and a freewheeling diode D1, where the freewheeling diode D1 is required to freewheel when the load 200 is an inductive load, or the freewheeling diode D1 may be absent when the load 200 is a pure resistive or capacitive load.

In fig. 3, the power driving circuit 100 is a low-side switching driving circuit, and fig. 2 shows a switching device S2 and a freewheeling diode D2, where the freewheeling diode D2 is required to freewheel when the load 200 is an inductive load, or the freewheeling diode D2 may be absent when the load 200 is a pure resistive or capacitive load.

In fig. 4 and 5, the power driving circuit 100 is a full bridge driving circuit with two different types, where S1, S2, S3, S4 are switching devices, and D3, D4 are freewheeling diodes.

After the structure of the power driving circuit is determined, the influence of the current at the output terminal of the power driving circuit on the equivalence relation between I1 and I2 when the power driving circuit is in an abnormal condition can be analyzed through the circuit structure, and as shown in fig. 6, the power driving circuit is taken as a low-side switch driving circuit as an example:

case 1: the first output terminal O1 of the power driving circuit 100 is externally shorted to a voltage higher than the original first output terminal O1 or externally injects a current into the first output terminal O1. Assuming that the injected current is I3, according to kirchhoff' S current law, whether the switching device S2 is turned on or off, there is always a current relationship I3 to I2 to I1. It can be seen that the larger I3, the larger the difference between I1 and I2;

case 2: the first output terminal O1 of the power driving circuit 100 is externally shorted to a voltage lower than the original first output terminal O1, or an external current is drawn from the first output terminal O1, and assuming that the drawn current is I4, no matter whether the switching device S2 is turned on or off, there is always a current relationship I4I 1-I2. It can be seen that the larger I4, the larger the difference between I1 and I2.

Case 3: the second output terminal O2 of the power driving circuit 100 is shorted from the outside to a voltage higher than the original second output terminal O2, or a current is injected into the second output terminal O2 from the outside, and assuming that the injected current is I5, no matter whether the switching device S2 is turned on or off, there is always a current relationship I5 — I2-I1. It can be seen that the larger I5, the larger the difference between I1 and I2.

Case 4: the second output terminal O2 of the power driving circuit 100 is shorted from the outside to a voltage lower than the original second output terminal O2, or a current is externally drawn from the second output terminal O2, and assuming that the drawn current is I6, no matter whether the switching device S2 is turned on or off, there is always a current relationship I6 — I1-I2. It can be seen that the larger I6, the larger the difference between I1 and I2.

The current information processing circuit 2 is a differential amplifier circuit, and collects the first voltage signal V_I1And a second voltage signal V_I2After circuit processing, the output voltage Vc is equal to V_REF+ (I1-I2) A, the amplification factor A is the amplification factor of the output voltage of the differential amplifier circuit relative to the input unbalanced current (I1-I2), V_REFThe default voltage is when the input unbalanced current (I1-I2) of the differential amplifier circuit is 0. If the power driving circuit and the load are normal, I1 is I2, and Vc is V_REF. If the load port encounters an abnormal condition, for example, the above-mentioned condition 1, a current I3 is injected into the power driving circuit from the first output terminal O1 through the external circuit, the circuit structure cannot satisfy the condition that I1 is I2, I3 is I2-I1, and the Vc voltage value deviates from the reference voltage V_REF。Vc＝V_REFThe larger I3A, I3, the deviation of Vc voltage from reference voltage V_REFThe greater the magnitude of (c).

Comparison diagnosis circuit 3 compares the voltageComparing Vc with a preset voltage range, and when Vc is within the preset voltage range>V_TH1When I1 is judged to be higher than I2 by the expected range, a first diagnostic signal Alarm1 is generated, when Vc<V_TH2When it is judged that I2 is higher than I1 by the expected range, a second diagnostic signal Alarm2 is generated. The first diagnostic signal Alarm1 and the second diagnostic signal Alarm2 may function as alarms. Referring to fig. 7 to 9, in the present embodiment, the upper limit V is preset_TH1And lower voltage limit V_TH2The determination method comprises the following steps:

1) determining the fluctuation range of the voltage Vc when the circuit works normally (I1-I2), wherein Vc is Vcnormal, and the Vcnormal is relative to V due to the nonidealities of the current sampling circuit and the current information processing circuit_REFFluctuation can be obtained according to circuit error analysis, and V can be satisfied within a defined working range_REFMIN<Vcnormal<V_REFMAX；

2) The minimum and maximum differences between I1 and I2 required to generate a diagnostic signal are determined. Wherein I_D1Is the minimum I1-I2 amplitude, namely V, required when triggering I1 to be larger than I2 alarm_TH1＝V_REFMAX+I_D1*A，I_D2Is the minimum I2-I1 amplitude, namely V, required when triggering I2 to be larger than I1 alarm_TH2＝V_REFMIN–I_D2*A；I_D3Is the maximum I1-I2 amplitude, namely V, required when triggering the alarm with the I1 being larger than the I2_TH1＝V_REFMIN+I_D3*A；I_D4The maximum I2-I1 amplitude, namely V, is required when the trigger I2 is larger than the alarm I1_TH2＝V_REFMAX–I_D4*A。

The circuit is at least I greater at I1 than I2_D1When, V may be triggered_TH1Generating a first diagnostic signal Alarm1, I2 being at least I greater than I1_D2When, V may be triggered_TH2And a second diagnostic signal Alarm2 is generated. Using this setting, it will be ensured that when the absolute value of the difference between I1 and I2 is less than I_D1And I_D2When the circuit is in use, the diagnosis signal is not triggered, so that the normal work of the circuit is ensured not to be disturbed; when the absolute value of the difference between I1 and I2 is larger than I_D3Or I_D4Only when the load is abnormal, the diagnostic circuit can normally respond to the abnormal load to generate a reportAnd (5) alarming.

The principles and operation of the present invention are described in more detail below with reference to two specific embodiments.

First embodiment

Please refer to fig. 10. In this embodiment, the load 200 is an inductive load, the switching device S2 may be a MOSFET, for example, and the freewheeling diode D2 provides a freewheeling path for the load when the switching device S2 is off.

The high-side current sampling circuit 11 comprises a current sampling resistor Shunt1, a current input end and a current output end of the current sampling resistor Shunt1 are respectively connected with the anode of the power Vin and a current inflow end a1 of the power driving circuit 100, and a first voltage signal V is output from the current input end and the current output end of the current sampling resistor Shunt1_I1. The low-side current sampling circuit 12 includes a current sampling resistor Shunt2, one end of the current sampling resistor Shunt2 is connected to the current outflow end a2 of the power driving circuit 100, the other end of the current sampling resistor Shunt2 is connected to the negative electrode of the power supply, and one end of the current sampling resistor Shunt2 outputs a second voltage signal V_I2。

The current information processing circuit 2 comprises an operational amplifier U1, a resistor R5, a resistor R6, a resistor network and a reference voltage source 21. The output voltage of the reference voltage source 21 is V_REFThe resistor network comprises a first series branch and a second series branch, the first series branch comprises a resistor R1 and a resistor R2 which are connected with each other in series, and the second series branch comprises a resistor R3 and a resistor R4 which are connected with each other in series. Two ends of the first series branch are respectively connected with a current input end P1 of a current sampling resistor Shunt1 and the negative electrode of a power supply Vin; two ends of the second series branch are respectively connected with the current output end P2 of the current sampling resistor Shunt1 and one end P3 of the current sampling resistor Shunt 2; a common junction point P4 of the resistor R1 and the resistor R2 is connected with a common junction point of one end of the resistor R6 and the non-inverting input end of the operational amplifier U1, and a common junction point P5 of the resistor R3 and the resistor R4 is connected with a common junction point of one end of the resistor R5 and the inverting input end of the operational amplifier U1; the other end of the resistor R5 is connected with the output end of the operational amplifier U1, the other end of the resistor R6 is connected with the anode of the reference voltage source 21, and the cathode of the reference voltage source 21 is connected with the cathode of the power Vin; output terminal of operational amplifier U1 andthe input of the comparative diagnostic circuit 3 is connected.

The current sampling resistors Shunt1 and Shunt2 are precision current sampling resistors, and the resistance values of the precision current sampling resistors are in the level of tens of mOhm, which is 50mOhm in the embodiment. The resistor R1, the resistor R2, the resistor R3 and the resistor R4 form a resistor network, and their resistance values are in KOhm level, which is 10KOhm in this embodiment. The internal resistance of the voltage signals of the current sampling resistor Shunt1 and the current sampling resistor Shunt2 is much smaller than that of the resistor network, and it can be approximated that the current flowing through the current sampling resistor Shunt1 flows through the first output terminal O1, and the current flowing through the current sampling resistor Shunt2 flows through the second output terminal O2. The current in the circuit is shown in the figure, I1 is the current flowing through the current sampling resistor Shunt1, I2 is the current flowing through the current sampling resistor Shunt2, Iout is the current flowing through the load 200, and the arrow direction in the figure is defined as the positive direction of the current. Node P4 is connected to the non-inverting input of the op-amp U1 and node P5 is connected to the inverting input of the op-amp U1. The output of the current information processing circuit 2 is the output voltage signal Vc of the operational amplifier U1.

The comparison diagnosis circuit 3 is a window comparison circuit and includes voltage comparators U2, U3, a resistor R7, a resistor R8, a resistor R9, a resistor R10, and a resistor R11. The voltage comparator U2 and the voltage comparator U3 are output open drain/open collector voltage comparators, the output end of the voltage comparator U2 is pulled up to a 5V voltage source through a resistor R7, and the output end of the voltage comparator U3 is pulled up to another 5V voltage source through a resistor R11. VCC is a voltage source, a resistor R8, a resistor R9 and a resistor R10 form a voltage-dividing resistor network, and a proper upper voltage limit V can be obtained by adjusting the resistance values of the resistor R8, the resistor R9 and the resistor R10_TH1And lower voltage limit V_TH2. Lower voltage limit V_TH2Connected to the inverting input of a voltage comparator U3, and having an upper voltage limit V_TH1Is connected to the non-inverting input of the voltage comparator U2. The output terminal of the current information processing circuit 2 is connected to the inverting input terminal of the voltage comparator U2 and the non-inverting input terminal of U3, respectively. The function of the window comparison circuit is: when Vc is present>V_TH1Outputs a first diagnostic signal Alarm1 when Vc<V_TH2The second diagnosis signal Alarm2 is output, and the first diagnosis signal Alarm1 and the second diagnosis signal Alarm2 are both low levelA signal. In this embodiment, R1 ═ R2 ═ R3 ═ R4 ═ 10K, the operational amplifier U1 uses the common voltage operational amplifier of the company TI, model LM2904A, and the voltage comparators U2 and U3 use the voltage comparators of the company TI, model LM 2903. The operational amplifier U1, the voltage comparator U2 and the voltage comparator U3 are powered by a 10V single power supply. Reference voltage V_REFThe power amplifier is 5V, R5 is 100K, R6 is 100K, and the circuit closed loop amplification factor of the operational amplifier U1 is A_CL20. Resistance R of current sampling resistors Shunt1 and Shunt2_shunt1、R_shunt2Are all 50 mohm. In this embodiment, the amplification factor a of the output voltage Vc of the operational amplifier U1 with respect to the input unbalanced current (I1-I2) is a ═ a_CL*R_shunt1＝20*50mohm＝1，Vc＝V_REF(I1-I2) × 1 ═ 5+ (I1-I2), and according to the above analysis of normal operation and four abnormal conditions, the signal voltage of Vc is:

vccase1 to Vccase4 correspond to the voltage values of the output voltage Vc of the operational amplifier U1 under four abnormal conditions.

In the present embodiment, because of the special resistance of the resistor network, the output voltage Vcnormal of the current information processing circuit 2 under normal operation is the reference voltage V_REF(i.e., 5V), the upper voltage limit V of the window comparator circuit may be based on the normal range for Vcnormal and the magnitude of abnormal current that the circuit can tolerate_TH1And lower voltage limit V_TH2Is adjusted. When Vccase 1-Vccase 4 do not satisfy V_TH2<Vccase1、Vccase2、Vccase3、Vccase4<V_TH1And when the window comparison circuit outputs low level, an alarm is generated. The analysis of the normal range for Vcnormal in this example is as follows: in the ideal case, Vcnormal in this embodiment is always equal to the reference voltage V_REFIndependent of Iout and Vin. In a practical circuit, Vcnormal is relative to V in consideration of resistance precision, resistance value drift and non-ideality of operational amplifier_REFThere is an error. The inputs for the error analysis are that the maximum procurement error of the resistor R5 and the resistor R6 is +/-1%, and the maximum drift error in the life cycle is +/-2%Total maximum error. + -. 3%. The resistors R1, R2, R3 and R4 are 10K thin film resistor arrays of type ACASA1000S1000P1AT by VISHAY. Their relative accuracy over the life cycle is 0.125% and absolute accuracy is 0.25%. The maximum input offset voltage Vos of the operational amplifier LM2904A is +/-4 mV, the error of the current sampling resistors Shunt1 and Shunt2 is +/-1%, and the introduced differential mode signal V_DTOLThe error is + -2.5 mV. For reasons of resistance error, the above-mentioned condition of R1 ═ R2 ═ R3 ═ R4 has not been satisfied, and the formula of Vcnormal is updated as:

for error estimation, R1, R2, R3, R4, R5, R6 in the formula can be respectively recorded as

R1 ═ 10k ═ 1+ tolr1, R2 ═ 10k ═ 1+ tolr2, R3 ═ 10k ═ 1+ tolr3, R4 ═ 10k ═ 1+ tolr4, R5 ═ 100k × (1+ tolr5), R6 ═ 100k ═ 1+ tolr 6. Wherein: -0.25% < tolr1, tolr2, tolr3, tolr4 < 0.25%, -3% < tolr5, tolr6 < 3%. tolr1 to tolr6 are deviations of the actual resistance values of the resistors R1 to R6, respectively, from the nominal resistance values.

Vcnormal takes a maximum value V_REFMAXAnd a minimum value V_REFMINThe conditions of (a) are as follows:

set V_TH1And V_TH2The value of (c): assuming that the abnormal current protection circuit can resist at least 2 amperes of unbalanced current, i.e. when | I1-I2 |)<2A, the diagnostic signal is not triggered and V can be set_TH1＝V_REFMAX+2*A＝7.76V，V_TH1＝V_REFMIN2a 2.21V, the values of the resistor R8, the resistor R9 and the resistor R10 can be adjusted to obtain the designed V_TH1And V_TH2A voltage. Vc when abnormality occurs in the drive circuit>V_TH1Then, a first diagnostic signal Alarm1 is generated, when Vc<V_TH2Then a second diagnostic signal, Alarm2, is generated.

Second embodiment

Referring to fig. 11, in the present embodiment, the structure of the power driving circuit 100 is the same as that of the first embodiment.

The high-end current sampling circuit comprises a current sampling resistor Shunt31, a resistor R31, a resistor R32, a resistor R33, a resistor R34, an operational amplifier U34 and an NPN triode T1. The current input end and the current output end of the current sampling resistor Shunt31 are respectively connected with the anode of the power source Vin and the current inflow end A1 of the power driving circuit 100; one end of the resistor R31 is connected with a current input end P31 of the current sampling resistor Shunt31, and the other end of the resistor R31 is connected with a common junction P34 of a non-inverting input end of the operational amplifier U34 and a collector of the NPN triode T1; one end of the resistor R32 is connected to the current output end P32 of the current sampling resistor Shunt31, and the other end of the resistor R32 is connected to the inverting input end of the operational amplifier U34; the base of the NPN triode T1 is connected with the output end of the operational amplifier U34 through a resistor R33, the emitter of the NPN triode T1 is connected with the negative electrode of the power Vin through a resistor R34, and the common junction P35 of the emitter of the NPN triode T1 and the resistor R34 outputs a first voltage signal V_I1。

The low-side current sampling circuit comprises a current sampling resistor Shunt32, one end of a current sampling resistor Shunt32 is connected with a current outflow end A2 of the power driving circuit, the other end of the current sampling resistor Shunt32 is connected with the negative electrode of a power supply Vin, and one end of the current sampling resistor Shunt32 outputs a second voltage signal V_I2。

In this embodiment, the current sampling resistors Shunt31 and Shunt32 are precision current sampling resistors and have resistance values of 20mOhm (milliohm). The resistor R31, the resistor R32, the resistor R33 and the resistor R34 are common resistors, the resistance values of the resistor R31, the resistor R32 and the resistor R34 are 100Ohm, and the resistance value of the resistor R33 is 1 Kohm. The operational amplifier U34 is a general voltage operational amplifier of TI company, and is of model LM2904A, and the NPN triode T1 is of model BC 817.

When a forward current I1 flows through the current sampling resistor Shunt31, the output end of the operational amplifier U34 passes throughThe circuit of the resistor R33, the resistor R31, the NPN triode T1 and the resistor R34 influences the voltage of the non-inverting input end to form negative feedback. The operational amplifier U34 drives the base current of the NPN transistor T1 in the range where negative feedback is available, so that the net input voltage at the non-inverting and inverting inputs of the operational amplifier U34 is very close to 0V. Neglecting the currents flowing into the non-inverting and inverting inputs of the operational amplifier U34 (because they are only on the order of tens of nA), the voltage drop across the resistor R32 is about 0V, and V is available_P32＝V_P34，V_Shunt31＝V_R31. The collector current amplification of the NPN transistor T1 is 200 or more, and it can be considered that the collector current is approximately equal to the emitter current, i.e., the current flowing through the resistor R31 from the node P31 to the node P34 is equal to the current flowing through the resistor R34 from the node P35. The resistor R31 and the resistor R34 have the same resistance value, and the voltage drop across them is also equal, i.e. V_R34＝V_R31＝V_Shunt31The circuit converts the voltage drop across the current sampling resistor Shunt31 to resistor R34. The current I1 and current I2 signals are converted into a voltage signal V relative to ground_P35And V_P33And the subsequent circuit processing is convenient.

The current information processing circuit is a differential amplifying circuit, the differential amplifying circuit comprises an operational amplifier U31, a resistor R35, a resistor R36, a resistor R37, a resistor R38 and a reference voltage source 22, and the output voltage of the reference voltage source is V_REF. In a second embodiment, the output voltage V of the reference voltage source_REF2.5V, while the output voltage V of the reference voltage source in the first embodiment is_REF Is 5V.

One end of the resistor R35 is connected to a common junction P35 between the emitter of the NPN transistor T1 and the resistor R34, the other end of the resistor R35 is connected to a common junction between the non-inverting input end of the operational amplifier U31 and one end of the resistor R36, the other end of the resistor R36 is connected to the anode of the reference voltage source 22, and the cathode of the reference voltage source 22 is connected to the cathode of the power source Vin. One end of the resistor R37 is connected with one end P33 of the current sampling resistor Shunt32, the other end of the resistor R37 is connected with the common junction point of the inverting input end of the operational amplifier U31 and one end of the resistor R38, and the other end of the resistor R38 is connected with the output end of the operational amplifier U31; the output end of the operational amplifier U31 is connected with the input end of the comparison diagnosis circuit 3.

The resistors R35 and R37 are common resistors with resistance values of 3.3Kohm, and the resistors R36 and R38 are common resistors with resistance values of 100 Kohm. The reference voltage source 22 is a 2.5V voltage source. The operational amplifier U31 is a general voltage operational amplifier of TI company, and is in the model number LM 2904A. The output of the operational amplifier U31 is Vc-V_REF+(V_P35-V_P33)*A_CLI.e. Vc ═ V_REF+(I1-I2)*20mohm*A_CLWherein A is_CLIs the DC closed loop amplification factor of the operational amplifier U1, A_CL＝30.3。

The comparison diagnosis circuit 3 is a window comparison circuit and includes voltage comparators U2, U3, a resistor R39, a resistor R40, a resistor R41, a resistor R42, and a resistor R43. The voltage comparator U2 and the voltage comparator U3 are voltage comparators of TI company, model LM2903, the output end of the voltage comparator U2 is pulled up to a 5V voltage source through a resistor R42, and the output end of the voltage comparator U3 is pulled up to a 5V voltage source through a resistor R43. VCC is a 5V voltage source, a resistor R39, a resistor R40 and a resistor R41 form a voltage dividing resistor network, and a proper upper voltage limit V can be obtained by adjusting the resistance values of the resistor R39, the resistor R40 and the resistor R41_TH1And lower voltage limit V_TH2. Lower voltage limit V_TH2Connected to the inverting input of a voltage comparator U3, and having an upper voltage limit V_TH1Is connected to the non-inverting input of the voltage comparator U2. The output terminal of the current information processing circuit 2 is connected to the inverting input terminal of the voltage comparator U2 and the non-inverting input terminal of the voltage comparator U3, respectively. The function of the window comparison circuit is: when Vc is present>V_TH1Outputs a first diagnostic signal Alarm1 when Vc<V_TH2The second diagnostic signal Alarm2 is output, and the first diagnostic signal Alarm1 and the second diagnostic signal Alarm2 are both low level signals.

The maximum and minimum variation range of Vcnormal under normal conditions is analyzed. Error sources for Vcnormal are: resistance errors of current sampling resistors Shunt31, Shunt 32: plus or minus 1 percent; input offset voltage Vos of the operational amplifier U31 and the operational amplifier U34: +/-4 mV; absolute error of R31, R34, resistor R35, resistor R36, resistor R37, and resistor R38: plus or minus 3 percent; unequal errors of collector and emitter currents of the NPN triode T1; the error caused by the load effect of the input resistance of the differential amplification circuit on the input signal source is smaller than the error and is ignored in the analysis.

The maximum range of the currents I1, I2 is assumed to be 10A.

Set V_TH1And V_TH2The value of (c): assuming that the abnormal current protection circuit can resist the unbalance current of 1 ampere at least, i.e. when | I1-I2 |)<1A, the first and second diagnostic signals Alarm1 and Alarm2 are not triggered, and V can be set_TH1＝V_REFMAX+1*20m*A_CL＝4.17V，V_TH1＝V_REFMIN-2*20m*A_CLThe value of the resistors R39, R40, R41 can be adjusted to 0.95V to obtain a designed V_TH1And V_TH2A voltage. Vc is caused when abnormality occurs in the power driving circuit>V_TH1Outputs a first diagnostic signal Alarm1, Vc<V_TH2A second diagnostic signal Alarm2 is output.

In the first embodiment, the second voltage signal V_I2Referenced to ground, a first voltage signal V_I1Is superposed on the power supply voltage, and the difference value of two voltages is collected by a current information processing circuit, and a first voltage signal V_I1Essentially a weak differential mode signal superimposed on a high common mode voltage. For normal circuit function, the resistors R1, R2, R3 and R4 of the resistor network in the first embodiment need to adopt high-precision resistors, otherwise, high common-mode voltage can affect the output voltage V through the error of the resistor network_C. In the second embodiment, the circuit including the operational amplifier U34 and the NPN transistor T1 is provided to improve the problemA voltage signal V_I1The signal becomes the signal of the reference ground, and the interference of the common-mode signal is eliminated, so the error requirement of the resistance of the second embodiment is not higher than that of the first embodiment.

It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the utility model. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.

Claims

1. A diagnostic circuit for a power driving circuit, the power driving circuit comprising a current inflow terminal, a current outflow terminal, a first output terminal and a second output terminal; the current inflow end and the current outflow end are respectively used for being connected to the positive pole and the negative pole of a power supply, and the first output end and the second output end are respectively used for being connected with the first end and the second end of a load; wherein the diagnostic circuit comprises:

a current sampling circuit for collecting the current I1 flowing into the current inflow end of the power driving circuit from the anode of the power supply and outputting a first voltage signal V related to the current I1_I1And collecting a current I2 flowing from a current outflow end of the power driving circuit to the negative electrode of the power supply and outputting a second voltage signal V related to the current I2_I2；

The input end of the current information processing circuit is connected with the output end of the current sampling circuit and is used for processing a first voltage signal V_I1And a second voltage signal V_I2Processed to output voltage Vc, Vc ═ V_REF+(I1-I2)*A，V_REFIs a reference voltage, and A is a magnification factor;

the input end of the comparison diagnosis circuit is connected with the output end of the current information processing circuit and is used for judging whether the voltage Vc is greater than a preset upper voltage limit V_TH1And whether it is less than the preset lower voltage limit V_TH2At Vc greater than V_TH1Generating a first diagnostic signal when Vc is less than V_TH2A second diagnostic signal is generated.

2. The diagnostic circuit of a power driver circuit of claim 1, wherein the current sampling circuit comprises a high-side current sampling circuit and a low-side current sampling circuit;

the high-end current sampling circuit comprises a current sampling resistor Shunt31, a resistor R31, a resistor R32, a resistor R33, a resistor R34, an operational amplifier U34 and an NPN triode T1; the current input end and the current output end of the current sampling resistor Shunt31 are respectively connected with the anode of the power supply and the current inflow end of the power driving circuit; one end of the resistor R31 is connected with the current input end of the current sampling resistor Shunt31, and the other end of the resistor R31 is connected with the common junction of the non-inverting input end of the operational amplifier U34 and the collector of the NPN triode T1; one end of the resistor R32 is connected with the current output end of the current sampling resistor Shunt31, and the other end of the resistor R32 is connected with the inverting input end of the operational amplifier U34; the base of the NPN triode T1 is connected with the output end of the operational amplifier U34 through a resistor R33, the emitter of the NPN triode T1 is connected with the negative electrode of the power supply through a resistor R34, and the common joint of the emitter of the NPN triode T1 and the resistor R34 outputs a first voltage signal V_I1；

The low-side current sampling circuit comprises a current sampling resistor Shunt32, one end of a current sampling resistor Shunt32 is connected with the current output end of the power driving circuit, the other end of the current sampling resistor Shunt32 is connected with the negative electrode of the power supply, and one end of a current sampling resistor Shunt32 outputs a second voltage signal V_I2。

3. The diagnostic circuit of the power driving circuit as claimed in claim 2, wherein the resistance R31 is equal to the resistance R34.

4. The diagnostic circuit of the power driving circuit according to claim 2, wherein the current information processing circuit is a differential amplifier circuit comprising an operational amplifier U31, a resistor R35, a resistor R36, a resistor R37, a resistor R38, and a reference voltage source, the reference voltage source havingOutput voltage of V_REF；

One end of the resistor R35 is connected to a common junction point of an emitter of the NPN triode T1 and the resistor R34, the other end of the resistor R35 is connected to a common junction point of a non-inverting input end of the operational amplifier U31 and one end of the resistor R36, the other end of the resistor R36 is connected with the anode of the reference voltage source, and the cathode of the reference voltage source is connected to the cathode of the power supply; one end of the resistor R37 is connected with one end of the current sampling resistor Shunt32, the other end of the resistor R37 is connected with the common junction of the inverting input end of the operational amplifier U31 and one end of the resistor R38, and the other end of the resistor R38 is connected with the output end of the operational amplifier U31; the output end of the operational amplifier U31 is connected with the input end of the comparison diagnosis circuit.

5. The diagnostic circuit of a power driver circuit of claim 1, wherein the current sampling circuit comprises a high-side current sampling circuit and a low-side current sampling circuit;

the high-end current sampling circuit comprises a current sampling resistor Shunt1, a current input end and a current output end of the current sampling resistor Shunt1 are respectively connected with the anode of the power supply and the current inflow end of the power driving circuit, and a first voltage signal V is output from the current input end and the current output end of the current sampling resistor Shunt1_I1；

The low-side current sampling circuit comprises a current sampling resistor Shunt2, one end of a current sampling resistor Shunt2 is connected with a current outflow end of the power driving circuit, the other end of the current sampling resistor Shunt2 is connected with the negative electrode of the power supply, and one end of a current sampling resistor Shunt2 outputs a second voltage signal V_I2。

6. The diagnostic circuit of the power driving circuit according to claim 5, wherein the current information processing circuit comprises an operational amplifier U1, a resistor R5, a resistor R6, a resistor network and a reference voltage source, and the output voltage of the reference voltage source is V_REFThe resistance network comprises a first series branch comprising a resistance R1 and a resistance R2 connected in series with each other, and a second series branchThe circuit comprises a resistor R3 and a resistor R4 which are connected with each other in series;

two ends of the first series branch are respectively connected with a current input end of a current sampling resistor Shunt1 and the negative electrode of the power supply; two ends of the second series branch are respectively connected with the current output end of the current sampling resistor Shunt1 and one end of the current sampling resistor Shunt 2; a common junction of the resistor R1 and the resistor R2 is connected with a common junction of one end of the resistor R6 and a non-inverting input end of the operational amplifier U1, and a common junction of the resistor R3 and the resistor R4 is connected with a common junction of one end of the resistor R5 and an inverting input end of the operational amplifier U1; the other end of the resistor R5 is connected with the output end of the operational amplifier U1, the other end of the resistor R6 is connected with the anode of the reference voltage source, and the cathode of the reference voltage source is connected with the cathode of the power supply; the output end of the operational amplifier U1 is connected with the input end of the comparison diagnosis circuit.

7. The diagnostic circuit of the power driving circuit according to claim 6, wherein the resistances of the resistor R1, the resistor R2, the resistor R3 and the resistor R4 are respectively 10 Kohm;

the resistances of the current sampling resistor Shunt1 and the current sampling resistor Shunt2 are 50mohm respectively.

8. The power driver circuit of any one of claims 1 to 7, wherein the comparison diagnostic circuit is a window comparator circuit.

9. The power driver circuit of claim 1, wherein the first diagnostic signal and the second diagnostic signal are level signals.