Low-voltage detection circuit for PSI5 protocol synchronization pulse signal

Abstract

The invention relates to a low-voltage detection circuit for a PSI5 protocol synchronous pulse signal. The low-voltage detection circuit comprises a transient circuit, a steady-state circuit, a comparison threshold value generation circuit and a low-voltage power supply end for providing a low-voltage stabilized power supply signal. The transient circuit generates a transient voltage signal and a transient current signal according to a power supply voltage signal, a synchronous pulse signal and a first reference voltage. The steady-state circuit generates a steady-state voltage signal according to the transient voltage signal. The comparison threshold generation circuit generates a comparison threshold current signal according to the steady-state voltage signal and a second reference voltage. And when the distance between the output end of the transient circuit and the output end of the comparison threshold generation circuit is one half of the low-voltage stabilized power supply signal, the transient current signal is equal to the comparison threshold current signal, so that the detected synchronous pulse signal is irrelevant to the power supply voltage signal. Therefore, high accuracy of low-level detection of the synchronization pulse signal is ensured. Compared with the prior art of high-voltage detection, the circuit is simple in structure, high in reliability and low in cost.

Description

Technical Field

[0001] The invention relates to the field of signal detection, and in particular to a low-voltage detection circuit for a PSI5 protocol synchronous pulse signal. Background Art

[0002] The PSI5 (Peripheral Sensor Interface 5) protocol is an open communication protocol for automotive sensors. This protocol is well-known for its robust anti-interference characteristics and was originally used in airbag systems. However, with the development of technology, the application of the PSI5 protocol is no longer limited to this, and it is now increasingly being used in new sensor-intensive automotive applications.

[0003] like Figure 1 As shown in the figure, it is the bus topology of the PSI5 protocol. In this structure, the ECU (Electronic Control Unit) includes two output terminals, one of which is connected to VCC and the other is connected to VSS; one or more sensors are connected to the ECU (Electronic Control Unit) in parallel; in the synchronous mode, the ECU controls the synchronous pulse signal modulated on the power supply voltage signal, and one or more sensors respond to the synchronous pulse signal generated by the ECU and start to send data according to their corresponding time slots. Among them, the signal waveform of the synchronous pulse signal modulated on the power supply voltage signal by the ECU is as follows: Figure 2 As shown, V supply is the normal power supply voltage signal provided by the ECU, V sync It is the synchronization pulse signal sent by ECU.

[0004] According to the PSI5 protocol, the power supply voltage signal is allowed to vary within a wide range, which is between 5V and 16.5V. The synchronization pulse signal is a high pulse signal with a fixed amplitude relative to the power supply voltage signal, and its voltage range is between 4V and 5V. Since the power supply voltage signal floats within the range of 5V to 16.5V, the low potential of the synchronization pulse signal is uncertain, which means that the synchronization pulse signal is also floating.

[0005] In the related art, in order to detect a certain synchronization pulse signal, a high-voltage detection circuit needs to be used. However, the circuit structure is complex and the reliability is low. Summary of the invention

[0006] The present invention provides a low voltage detection circuit for a PSI5 protocol synchronous pulse signal to solve at least one of the above technical problems.

[0007] The technical solution of the present invention to solve the above technical problem is as follows: a low voltage detection circuit for a PSI5 protocol synchronous pulse signal, comprising: A voltage input terminal for connecting to the PSI5 protocol, wherein the voltage input terminal inputs a power supply voltage signal and a synchronization pulse signal; A first reference voltage terminal, used for connecting to a first reference voltage; a transient circuit, connected to the voltage input terminal and the first reference voltage terminal, and configured to generate a transient voltage signal and a transient current signal according to the supply voltage signal, the synchronization pulse signal and the first reference voltage; A steady-state circuit, connected to the transient circuit, for performing steady-state processing on the transient voltage signal to generate a steady-state voltage signal; A second reference voltage terminal, used for connecting to a second reference voltage; a comparison threshold generating circuit, connected to the steady-state circuit, the second reference voltage terminal and the transient circuit, and configured to generate a comparison threshold current signal according to the steady-state voltage signal and the second reference voltage; A low voltage power supply terminal, connected to the comparison threshold generating circuit, for providing a low voltage regulated power supply signal; When the voltage signal between the output end of the transient circuit and the output end of the comparison threshold generating circuit is half of the low voltage regulated power supply signal, the transient current signal is equal to the comparison threshold current signal, so that the detected synchronization pulse signal is independent of the power supply voltage signal.

[0008] Based on the above technical solution, the present invention can also be improved as follows.

[0009] Furthermore, the transient circuit, the steady-state circuit and the comparison threshold generating circuit all use the ground potential as a reference.

[0010] Further, the transient circuit comprises: a first feedback circuit, connected to the voltage input terminal and the first reference voltage terminal, and configured to generate a transient voltage signal and an initial transient current signal according to the power supply voltage signal, the synchronization pulse signal and the first reference voltage; The first mirror circuit is connected to the first feedback circuit and is used for mirroring the initial transient current signal by K times according to the transient voltage signal to generate the transient current signal.

[0011] Further, the first feedback circuit includes: A first resistor, one end of which is connected to the voltage input end; a first operational amplifier, having a non-inverting input terminal connected to the other end of the first resistor and an inverting input terminal connected to the first reference voltage terminal, for making the voltage at the other end of the first resistor follow the first reference voltage, and generating the transient voltage signal according to the power supply voltage signal, the synchronization pulse signal and the first reference voltage; A first transistor, having a gate connected to the output end of the first operational amplifier, a drain connected to the other end of the first resistor, and a source grounded, is used to generate the initial transient current signal according to the transient voltage signal, the power supply voltage signal, the synchronization pulse signal and the first resistor.

[0012] Further, the first mirror circuit includes: a second transistor, having a gate connected to the gate of the first transistor, a drain connected to the comparison threshold generating circuit, and a source grounded; The size ratio of the second transistor to the first transistor is K:1, and is used to mirror the initial transient current signal by K times to generate the transient current signal.

[0013] Further, the comparison threshold generating circuit comprises: a second mirror circuit, connected to the steady-state circuit, for mirroring the average value of the transient current signal by 1 / K times according to the steady-state voltage signal to generate an initial steady-state current signal; a second feedback circuit, connected to the second reference voltage terminal, and generating a reference current signal according to the second reference voltage; a current accumulation circuit, connected to the second mirror circuit, the second feedback circuit and the low-voltage power supply terminal, and configured to sum the initial steady-state current signal and the reference current signal to generate an initial comparison threshold current signal; A third mirror circuit, connected to the current accumulation circuit, the transient circuit and the low-voltage power supply terminal, for mirroring the initial comparison threshold current signal by K times to generate the comparison threshold current signal; When the voltage signal between the output end of the transient circuit and the output end of the third mirror circuit is half of the low-voltage regulated power supply signal, the transient current signal is equal to the comparison threshold current signal, so that the detected synchronization pulse signal is independent of the power supply voltage signal.

[0014] Further, the second mirror circuit includes: The third transistor has a gate connected to the steady-state circuit, a drain connected to the current accumulation circuit, and a source connected to the ground, and is used to mirror the average value of the transient current signal by 1 / K times according to the steady-state voltage signal to generate an initial steady-state current signal.

[0015] Further, the second feedback circuit includes: A second resistor, one end of which is grounded; A second operational amplifier, having a non-inverting input terminal connected to the second reference voltage terminal and an inverting input terminal connected to the other end of the second resistor, for making the voltage at the other end of the second resistor follow the second reference voltage; A fourth transistor, having a gate connected to the output end of the second operational amplifier, a source connected to the other end of the second resistor, and a drain connected to the current accumulation circuit, is used to generate the reference current signal according to the second reference voltage, the second operational amplifier and the second resistor.

[0016] Further, the current accumulation circuit includes a fifth transistor, the drain of the fifth transistor is connected to the drain of the third transistor and the drain of the fourth transistor, the source of the fifth transistor is connected to the low-voltage power supply terminal, and the gate of the fifth transistor is short-circuited with its drain; The third mirror circuit includes a sixth transistor, a gate of the sixth transistor is connected to the gate of the fifth transistor, a source of the sixth transistor is connected to the low-voltage power supply terminal, and a drain of the sixth transistor is connected to the transient circuit; a size ratio of the sixth transistor to the fifth transistor is K:1, and is used to mirror the initial comparison threshold current signal by K times to generate the comparison threshold current signal.

[0017] Furthermore, it also includes a shaping circuit, which is connected to the transient circuit and the comparison threshold generating circuit, and is used to shape and output the synchronization pulse signal when the transient current signal is equal to the comparison threshold current signal.

[0018] The beneficial effects of the present invention are as follows: a low-voltage detection circuit of a PSI5 protocol synchronization pulse signal provided by the present invention adopts a transient circuit and a comparison threshold generation circuit to form a current comparator, wherein the signal generated by the transient circuit represents the instantaneous value of the power supply voltage signal and the synchronization pulse signal, and the signal generated by the comparison threshold generation circuit represents the steady-state value of the power supply voltage signal and the synchronization pulse signal. At the same time, a low-voltage stabilized power supply signal is adopted, so that at the flip point of the current comparator, the detected synchronization pulse signal is independent of the power supply voltage signal, thereby ensuring the high accuracy of the low-level detection of the synchronization pulse signal. In addition, all circuits work under a low-voltage stabilized power supply signal. Compared with the existing technology of high-voltage detection, the circuit structure of the present invention is simple, highly reliable and low-cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the bus topology structure based on the PSI5 protocol; Figure 2 The signal waveform diagram of the synchronous pulse signal modulated on the power supply voltage signal for ECU control; Figure 3 A structural block diagram of a low voltage detection circuit for a PSI5 protocol synchronous pulse signal provided by the present invention; Figure 4 A structural block diagram of another low-voltage detection circuit for a PSI5 protocol synchronous pulse signal provided by the present invention; Figure 5 A specific structural block diagram of another low-voltage detection circuit for a PSI5 protocol synchronous pulse signal provided by the present invention; Figure 6 for Figure 5 A specific circuit diagram of a low voltage detection circuit for a PSI5 protocol synchronous pulse signal shown; Figure 7 A waveform diagram of a power supply voltage signal and a synchronous pulse signal in a low voltage detection circuit of a PSI5 protocol synchronous pulse signal of the present invention; Figure 8 A current waveform diagram of a current flowing through a first transistor and a fifth transistor in a low voltage detection circuit of a PSI5 protocol synchronous pulse signal according to the present invention; Fig. 9 A waveform diagram of a comparison result signal in a low voltage detection circuit of a PSI5 protocol synchronous pulse signal according to the present invention; Fig.10 for Figure 5 Another specific circuit diagram of a low voltage detection circuit for a PSI5 protocol synchronous pulse signal is shown. DETAILED DESCRIPTION

[0020] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0021] like Figure 3 As shown, a low voltage detection circuit of a PSI5 protocol synchronous pulse signal includes: Used to connect to the voltage input terminal 1 of the PSI5 protocol, the voltage input terminal 1 inputs the supply voltage signal V supply and synchronization pulse signal V sync ; The first reference voltage terminal 2 is used to connect the first reference voltage V REF1 ; The transient circuit 3 is connected to the voltage input terminal 1 and the first reference voltage terminal 2 and is used for supply , the synchronization pulse signal V sync And the first reference voltage V REF1 Generate a transient voltage signal V1 and a transient current signal I1; A steady-state circuit 4, connected to the transient circuit 3, for performing steady-state processing on the transient voltage signal V1 to generate a steady-state voltage signal V2; The second reference voltage terminal 5 is used to connect the second reference voltage V REF2 ; The comparison threshold generating circuit 6 is connected to the steady-state circuit 4, the second reference voltage terminal 5 and the transient circuit 3, and is used to generate a comparison threshold value according to the steady-state voltage signal V2 and the second reference voltage V REF2 Generate a comparison threshold current signal I2; A low voltage power supply terminal 7, connected to the comparison threshold generating circuit 6, for providing a low voltage regulated power supply signal VDD; When the voltage signal between the output end of the transient circuit 3 and the output end of the comparison threshold generating circuit 6 is half of the low voltage regulated power supply signal VDD, the transient current signal I1 is equal to the comparison threshold current signal I2, so that the detected synchronization pulse signal V sync With the supply voltage signal V supply Not relevant.

[0022] The present invention uses a transient circuit 3 and a comparison threshold generating circuit 6 to form a current comparator, wherein the signal generated by the transient circuit 3 represents the supply voltage signal V supply and synchronization pulse signal V sync The instantaneous value of the comparison threshold generating circuit 6 generates a signal representing the supply voltage signal V supply and synchronization pulse signal V sync At the same time, a low voltage regulated power supply signal VDD is used. Therefore, at the flip point of the current comparator, that is, the point where the transient current signal I1 is equal to the comparison threshold current signal I2, the detected synchronization pulse signal V sync With the supply voltage signal V supply irrelevant, thus ensuring the synchronization pulse signal V sync The low level detection has high accuracy. Moreover, all circuits work under the low voltage regulated power supply signal VDD. Compared with the prior art of high voltage detection, the circuit structure of the present invention is simple, reliable and low cost.

[0023] In some embodiments, the transient circuit 3 , the steady-state circuit 4 , and the comparison threshold generating circuit 6 are all referenced to the ground potential.

[0024] Specifically, Figure 4 As shown, the transient circuit 3, the steady-state circuit 4 and the comparison threshold generating circuit 6 are all grounded, and are all based on the ground potential. The advantage of such a design is that there is no floating reference voltage in the circuit, thereby reducing interference and achieving the purpose of being insensitive to interference.

[0025] In some embodiments, Figure 5 As shown, the transient circuit 3 includes: The first feedback circuit 31 is connected to the voltage input terminal 1 and the first reference voltage terminal 2, and is used for generating a feedback signal according to the supply voltage signal V supply , the synchronization pulse signal V sync and the first reference voltage V REF1 Generate a transient voltage signal V1 and an initial transient current signal I1'; The first mirror circuit 32 is connected to the first feedback circuit 31 and is used for mirroring the initial transient current signal I1 ′ by K times according to the transient voltage signal V1 to generate the transient current signal I1 .

[0026] Specifically, the transient voltage signal V1 and the initial transient current signal I1' are both based on the power supply voltage signal V supply and synchronization pulse signal V sync Therefore, the transient voltage signal V1 and the initial transient current signal I1′ generated by the first feedback circuit 31 both represent the supply voltage signal V supply and synchronization pulse signal V sync The first mirror circuit 32 uses the current mirror principle to easily and accurately copy the initial transient current signal I1', and the resulting transient current signal I1 also represents the supply voltage signal V supply and synchronization pulse signal V sync The instantaneous value of .

[0027] In some embodiments, Figure 5 As shown, the comparison threshold generating circuit 6 includes: A second mirror circuit 61, connected to the steady-state circuit 4, for mirroring the average value of the transient current signal I1 by 1 / K times according to the steady-state voltage signal V2 to generate an initial steady-state current signal I1''; The second feedback circuit 62 is connected to the second reference voltage terminal 5 and generates a feedback signal according to the second reference voltage V REF2 Generate reference current signal I REF ; The current accumulation circuit 63 is connected to the second mirror circuit 61, the second feedback circuit 62 and the low-voltage power supply terminal 7, and is used to calculate the initial steady-state current signal I1'' and the reference current signal I REF Performing summation to generate an initial comparison threshold current signal I2'; A third mirror circuit 64, connected to the current accumulation circuit 63, the transient circuit 3 and the low-voltage power supply terminal 7, for mirroring the initial comparison threshold current signal I2' by K times to generate the comparison threshold current signal I2; When the voltage signal between the output end of the transient circuit 3 and the output end of the third mirror circuit 64 is half of the low voltage regulated power supply signal VDD, the transient current signal I1 is equal to the comparison threshold current signal I2, so that the detected synchronization pulse signal V sync With the supply voltage signal V supply Not relevant.

[0028] Specifically, since the steady-state voltage signal V2 is obtained by performing steady-state processing on the transient voltage signal V1, the steady-state voltage signal V2 can represent the steady-state value of the transient voltage signal V1, and since the transient voltage signal V1 is used to represent the steady-state value of the power supply voltage signal V supply and synchronization pulse signal V sync The instantaneous value of the steady-state voltage signal V2 can be used to characterize the power supply voltage signal V supply and synchronization pulse signal V sync steady-state value.

[0029] The transient circuit 3 and the comparison threshold generation circuit 6 cooperate to form a current comparator, and the working principle of the current comparator is to compare the real-time signal with the fixed reference signal to obtain a comparison result. The real-time signal here is the power supply voltage signal V supply and synchronization pulse signal V sync In order to obtain the fixed reference signal here, the present invention uses the second feedback circuit 62 to generate the reference current signal I REF ; However, the supply voltage signal V supply is floating, in order to avoid floating supply voltage signal V supply For the synchronization pulse signal V sync The present invention uses the reference current signal I REF The power supply voltage signal V supply and synchronization pulse signal V sync The steady-state voltage signal V2 of the steady-state value is superimposed to obtain the initial comparison threshold current signal I2', which also represents the supply voltage signal V supply and synchronization pulse signal V sync steady-state value.

[0030] In order to ensure the comparison accuracy of the current comparator, the two compared signals need to have the same amplification factor. Because the transient current signal I1 obtained in the transient circuit 3 is a measure of the power supply voltage signal V supply and synchronization pulse signal V sync The initial transient current signal I1' of the instantaneous value is K times mirrored, so it is also necessary to mirror the power supply voltage signal V supply and synchronization pulse signal V syncThe initial comparison threshold current signal I2' of the steady-state value is mirror-copied by the same multiple to obtain the comparison threshold current signal I2. The present invention amplifies the initial transient current signal I1' and the initial comparison threshold current signal I2' by the same multiple to obtain the transient current signal I1 and the comparison threshold current signal I2 accordingly, and further compares the two, thereby improving the stability and reliability of the comparison result.

[0031] In some embodiments, Figure 6 As shown, the first feedback circuit 31 includes: A first resistor R1, one end of which is connected to the voltage input terminal 1; The first operational amplifier A1 has a non-inverting input terminal connected to the other end of the first resistor R1 and an inverting input terminal connected to the first reference voltage terminal 2, and is used to make the voltage at the other end of the first resistor R1 follow the first reference voltage V REF1 , and according to the supply voltage signal V supply , the synchronization pulse signal V sync and the first reference voltage V REF1 generating the transient voltage signal V1; The first transistor M1 has a gate connected to the output terminal of the first operational amplifier A1, a drain connected to the other end of the first resistor R1, and a source connected to the ground GND, and is used to generate a voltage signal according to the transient voltage signal V1 and the power supply voltage signal V supply , the synchronization pulse signal V sync The first resistor R1 generates the initial transient current signal I1 ′.

[0032] Specifically, one end of the first resistor R1 is connected to the voltage input terminal 1, and the power supply voltage signal V supply and synchronization pulse signal V sync The waveform is as Figure 7 As shown in the figure, the ECU modulates the synchronous pulse signal Vsync on the power supply voltage signal V supply The above constitutes the comprehensive signal V IN , so V IN =V supply +V sync The integrated signal VIN can be obtained from the sensor power supply end or the ECU power supply pulse signal output end, so one end of the first resistor R1 is connected to the sensor power supply end or the ECU power supply pulse signal output end.

[0033] The first resistor R1, the first operational amplifier A1 and the first transistor M1 form a first feedback circuit; the signal outputted from the output terminal of the first operational amplifier A1 depends on the transient value of the integrated signal VIN, so the transient voltage signal V1 represents the transient value of the integrated signal VIN. When the gain of the first operational amplifier A1 is large enough, the two input terminals of the first operational amplifier A1 are in a virtual short state; therefore, the potentials of the non-inverting input terminal and the inverting input terminal of the first operational amplifier A1 are almost the same; since the other end of the first resistor R1 is connected to the non-inverting input terminal of the first operational amplifier A1, and the inverting input terminal of the first operational amplifier A1 is connected to the first reference voltage V REF1 , so the voltage at the other end of the first resistor R1 is equal to the first reference voltage V REF1 ,Right now Figure 6 The voltage at point A is equal to the first reference voltage V REF1 . Select the first reference voltage V REF1 Ratio supply voltage signal V supply So the current I flowing through the first resistor R1 can be calculated. R1 , that is I R1 =(V IN –V REF1 ) / R1=(V supply +V sync –V REF1 ) / R1.

[0034] The transient voltage signal V1 outputted from the output terminal of the first operational amplifier A1 is connected to the gate of the first transistor M1, providing a turn-on voltage for the first transistor M1 to drive the first transistor M1 to work. Since the first transistor M1 is connected in series with the first resistor R1, the current I flowing through the first transistor M1 is M1 The current I flowing through the first resistor R1 R1 Equal, that is, I M1 =I R1 Therefore, the initial transient current signal I1′ generated by the first feedback circuit 31 is the current I flowing through the first resistor R1. R1 , that is, the current I flowing through the first transistor M1 M1 ; Therefore, I1'=I M1 =I R1 =(V IN –V REF1 ) / R1=(V supply +V sync –V REF1 ) / R1. The current I flowing through the first transistor M1 M1 The waveform is as Figure 8 Shown as solid line.

[0035] The first feedback circuit 31 works under a low-voltage power supply, and thus can be implemented using a few simple devices including a first resistor R1, a first operational amplifier A1, and a first transistor M1. Thus, the circuit structure is simple, easy to implement, and low in cost. Meanwhile, the first transistor M1 in the first feedback circuit 31 works under a low-voltage power supply, and has good reliability.

[0036] In some embodiments, Figure 6 As shown, the first mirror circuit 32 includes: A second transistor M2, having a gate connected to the gate of the first transistor M1, a drain connected to the comparison threshold generating circuit 6, and a source connected to the ground GND; The size ratio of the second transistor M2 to the first transistor M1 is K:1, and is used to mirror the initial transient current signal I1 ′ by K times according to the transient voltage signal V1 to generate the transient current signal I1 .

[0037] Specifically, the second transistor M2 and the first transistor M1 in the first feedback circuit 31 form a current mirror, and the magnitude of the current flowing through them is proportional to their sizes; therefore, the size ratio of the first transistor M1 to the second transistor M2 can be set to 1:K (K is a preset constant), so that the second transistor M2 can mirror the current I flowing through the first transistor M1 by K times. M1 .

[0038] The transient current signal I1 generated by the first mirror circuit 32 is the current I flowing through the second transistor M2. M2 Therefore, the transient current signal I1 is equal to K times I M1 , that is I M2 = K *I M1 = K *I1'.

[0039] The current I flowing through the second transistor M2 M2 The gate of the second transistor M2 is connected to the transient voltage signal V outputted by the output terminal of the first operational amplifier A1. 1 , while the transient voltage signal V 1 Depends on the integrated signal V IN The transient value of the transient current signal I1 therefore represents the integrated signal V IN The instantaneous value of .

[0040] The first mirror circuit 12 includes only one second transistor M2, and its circuit structure is simple, easy to implement and low in cost; meanwhile, the second transistor M2 works under a low voltage power supply, and its reliability is good.

[0041] In some embodiments, Figure 6 As shown, the second mirror circuit 61 includes: The third transistor M3 has a gate connected to the steady-state circuit 4, a drain connected to the current accumulation circuit 63, and a source connected to the ground GND, and is used to mirror the average value of the transient current signal I1 by 1 / K times according to the steady-state voltage signal V2 to generate an initial steady-state current signal I1''.

[0042] Specifically, the steady-state current signal I1″ generated by the second mirror circuit 61 is the current I flowing through the third transistor M3. M3 , that is, I1''=I M3 The third transistor M3 and the second transistor M2 form a current mirror, and the magnitude of the current flowing through them is proportional to their sizes; therefore, the size ratio of the second transistor M2 to the third transistor M3 can be set to K:1, so that the third transistor M3 can mirror the current I flowing through the second transistor M2 by 1 / K times. M2 The gate of the third transistor M3 is connected to the steady-state circuit 4, so the gate voltage of the third transistor M3 is the steady-state voltage signal V2, and the steady-state voltage signal V2 drives the third transistor M3 to work, so the current I flowing through the third transistor M3 is M3 Equal to 1 / K times I M2 The steady-state value of I M2 = K *I M1 , so the current I flowing through the third transistor M3 M3 =I flowing through the first transistor M1 M1 The steady-state value of I M3 = average(I M1 )=average[(V IN –V REF1 ) / R1]= average[(V supply +V sync –V REF1 ) / R1], Average represents the steady-state function, that is, the function of finding the average value. Since the synchronous pulse signal V sync In terms of time, it is just a narrow pulse, which accounts for a small proportion of the average value. Therefore, when calculating the current I flowing through the first transistor M1, M1 When the steady-state value is reached, the synchronous pulse signal V sync Ignore, so I M3 ≈(V supply –V REF1 ) / R1.

[0043] The second mirror circuit 61 only includes a third transistor M3, and its circuit structure is simple, easy to implement and low in cost; at the same time, the third transistor M3 works under a low-voltage power supply and has good reliability.

[0044] In some embodiments, Figure 6As shown, the second feedback circuit 62 includes: A second resistor R2, one end of which is grounded to GND; The second operational amplifier A2 has a non-inverting input terminal connected to the second reference voltage terminal 5 and an inverting input terminal connected to the other end of the second resistor R2, and is used to make the voltage at the other end of the second resistor R2 follow the second reference voltage V REF2 ; The fourth transistor M4 has a gate connected to the output terminal of the second operational amplifier A2, a source connected to the other end of the second resistor R2, and a drain connected to the current accumulation circuit 63, and is used to generate a current according to the second reference voltage V REF2 The second operational amplifier A2 and the second resistor R2 generate the reference current signal I REF .

[0045] Specifically, in the second feedback circuit 62, the signal outputted from the output terminal of the second operational amplifier A2 (ie Figure 6 The voltage signal V 3 ) depends on the second reference voltage V REF2 When the gain of the second operational amplifier A2 is large enough, the two input terminals of the second operational amplifier A2 are in a virtual short state; therefore, the potentials of the in-phase input terminal and the inverting input terminal of the second operational amplifier A2 are almost the same; since one end of the second resistor R2 is grounded and the other end is connected to the inverting input terminal of the second operational amplifier A2, the in-phase input terminal of the second operational amplifier A2 is connected to the second reference voltage V REF2 , so the voltage at the other end of the second resistor R2 is equal to the second reference voltage V REF2 ,Right now Figure 6 The voltage at point B is equal to the second reference voltage V REF2 Therefore, the current I flowing through the second resistor R2 can be calculated. R2 , that is I R2 =V REF2 / R2.

[0046] The output terminal of the second op amp A2 outputs a voltage signal V 3 The gate of the fourth transistor M4 is connected to provide a start voltage for the fourth transistor M4 to drive the fourth transistor M4 to work. Since the fourth transistor M4 is connected in series with the second resistor R2, the current I flowing through the fourth transistor M4 is M4 The current I flowing through the second resistor R2 R2 Equal, that is, I M4 =I R2 Therefore, the reference current signal I generated by the second feedback circuit 62 is REF is the current I flowing through the second resistor R2 R2 , that is, the current I flowing through the fourth transistor M4 M4 , that is I REF =IM4 =I R2 =V REF2 / R2.

[0047] The second feedback circuit 62 works under a low-voltage power supply, and thus can be implemented using a few simple devices including a second resistor R2, a second operational amplifier A2, and a fourth transistor M4. Thus, the circuit structure is simple, easy to implement, and low in cost. Meanwhile, the fourth transistor M4 in the second feedback circuit 62 works under a low-voltage power supply, and has good reliability.

[0048] In some embodiments, Figure 6 As shown, the current accumulation circuit 63 includes a fifth transistor M5, the drain of the fifth transistor M5 is connected to the drain of the third transistor M3 and the drain of the fourth transistor M4, the source of the fifth transistor M5 is connected to the low-voltage power supply terminal 7, and the gate of the fifth transistor M5 is short-circuited with its drain; The third mirror circuit 64 includes a sixth transistor M6, a gate of the sixth transistor M6 is connected to the gate of the fifth transistor M5, a source of the sixth transistor M6 is connected to the low-voltage power supply terminal 7, and a drain of the sixth transistor M6 is connected to the transient circuit 3; the size ratio of the sixth transistor M6 to the fifth transistor M5 is K:1, and is used to mirror the initial comparison threshold current signal I2' by K times to generate the comparison threshold current signal I2.

[0049] Specifically, the low voltage regulated signal VDD inputted by the low voltage power supply terminal 7 can be provided by the sensor. The fifth transistor M5 is connected to the third transistor M3 and the fourth transistor M4 at the same time, which is equivalent to the fifth transistor M5 being connected in series with the second mirror circuit 61 and the second feedback circuit 62; therefore, the current I flowing through the fifth transistor M5 is M5 = equal to the steady-state current signal I1″ in the second mirror circuit 61 and the reference current signal I in the second feedback circuit 62 REF The sum of I M5 =I1''+I REF =I M3 +I M4 =(V supply –V REF1 ) / R1 +V REF2 / R2. Since the initial comparison threshold current signal I2' is the current I flowing through the fifth transistor M5 M5 , so I2'=I M5 =I M3 +I M4 = (V supply –V REF1 ) / R1 +V REF2 / R2. Among them, the current I flowing through the fifth transistor M5M5 The waveform of Figure 8 The dashed line shown in .

[0050] The current accumulation circuit 63 realizes the current accumulation of the two branches through the fifth transistor M5, and its circuit structure is simple, easy to implement and low in cost; at the same time, the fifth transistor M5 works under a low-voltage power supply and has good reliability.

[0051] The sixth transistor M6 in the third mirror circuit 64 and the fifth transistor M5 in the current accumulating circuit 63 form a current mirror, and the magnitude of the current flowing through them is proportional to their sizes; therefore, the size ratio of the fifth transistor M5 to the sixth transistor M6 can be set to 1:K, so that the sixth transistor M6 mirrors the current I flowing through the fifth transistor M5 by K times. M5 Therefore, the current I flowing through the sixth transistor M6 M6 Equal to K times I M5 , that is I M6 = K *I M5 =K*(I M3 +I M4 )= K*[(V supply –V REF1 ) / R1+V REF2 / R2].

[0052] The comparison threshold current signal I2 is the current I flowing through the sixth transistor M6. M6 , which is used as the detection synchronization pulse signal V sync A comparison threshold; and according to I2=I M6 = K *I M5 =K*(I M3 +I M4 )= K*[(V supply –V REF1 ) / R1 +V REF2 / R2], it can be seen that the comparison threshold current signal I2 is determined by the supply voltage signal V supply Steady-state value and reference voltage V REF Decision. Figure 6 As shown, the third mirror circuit 64 and the first mirror circuit 32 are connected at point C to form a current comparator. The current magnitude of the third mirror circuit 64 and the first mirror circuit 32 determines the potential of point C. Specifically, when the potential of point C is exactly between VDD and GND (that is, the potential of point C is VDD / 2), I M6 = K *I M5 , I M2 = K *I M1 , and I1= I2 (i.e. I M6 =I M2 ); At this time, if I M1Increase, I M2 As the current increases, the potential at point C decreases, and vice versa. Therefore, we can get the following: Fig. 9 The comparison result signal Rx is the potential of point C. When the supply voltage signal V supply There is a synchronous pulse signal V sync When the potential at point C reverses, the waveform of the comparison result signal Rx is also the synchronous pulse signal V sync waveform.

[0053] At the current comparator flip point (comparison threshold), according to I M6 = K *I M5 , I M2 = K *I M1 , and I1= I2 (i.e. I M6 =I M2 ) can be obtained: V sync ≈V REF2 *R1 / R2; Therefore, it can be seen that the comparison threshold is related to the supply voltage signal V supply and the first reference voltage V REF1 It has nothing to do with the ratio of the first resistor R1 to the second resistor R2 and the second reference voltage V REF2 Therefore, the detected synchronization pulse signal V supply The accuracy is higher.

[0054] In some embodiments, Figure 6 As shown, the steady-state circuit 4 is specifically an RC filter, which includes: Filter resistor R FLT , one end of which is connected to the gate of the second transistor M2, and the other end of which is connected to the gate of the third transistor M3; Filter capacitor C FLT , one end is connected to the filter resistor R FLT The other end is connected to the ground.

[0055] The RC filter is used to perform steady-state processing on the transient voltage signal V1 (ie, to achieve averaging processing through filtering); the RC filter is used as the steady-state circuit 4, which has a simple circuit structure, is easy to implement and has low cost.

[0056] In some embodiments, Figure 5 As shown, the low voltage detection circuit of the present invention further includes a shaping circuit 8, which is connected to the transient circuit 3 and the comparison threshold generating circuit 6, and is used to shape and output the synchronization pulse signal V when the transient current signal I1 is equal to the comparison threshold current signal I2. sync .

[0057] Specifically, Fig.10 As shown, the shaping circuit 8 is specifically a Schmitt trigger X0. The Schmitt trigger X0 shapes the voltage at point C to avoid distortion and noise interference, thereby obtaining a more accurate and stable signal, and thus making the shaped comparison result signal Rx and the synchronization pulse signal V sync Basically remain consistent.

[0058] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A low voltage detection circuit for a PSI5 protocol synchronous pulse signal, characterized in that: include: A voltage input terminal for connecting to the PSI5 protocol, wherein the voltage input terminal inputs a power supply voltage signal and a synchronization pulse signal; A first reference voltage terminal, used for connecting to a first reference voltage; a transient circuit, connected to the voltage input terminal and the first reference voltage terminal, and configured to generate a transient voltage signal and a transient current signal according to the supply voltage signal, the synchronization pulse signal and the first reference voltage; A steady-state circuit, connected to the transient circuit, for performing steady-state processing on the transient voltage signal to generate a steady-state voltage signal; A second reference voltage terminal, used for connecting to a second reference voltage; a comparison threshold generating circuit, connected to the steady-state circuit, the second reference voltage terminal and the transient circuit, and configured to generate a comparison threshold current signal according to the steady-state voltage signal and the second reference voltage; A low voltage power supply terminal, connected to the comparison threshold generating circuit, for providing a low voltage stabilized power supply signal; When the voltage signal between the output end of the transient circuit and the output end of the comparison threshold generating circuit is half of the low voltage regulated power supply signal, the transient current signal is equal to the comparison threshold current signal, so that the detected synchronization pulse signal is independent of the power supply voltage signal.

2. The low voltage detection circuit of the PSI5 protocol synchronization pulse signal according to claim 1, characterized in that: The transient circuit, the steady-state circuit and the comparison threshold generating circuit all use the ground potential as a reference.

3. The low voltage detection circuit of the PSI5 protocol synchronization pulse signal according to claim 1, characterized in that: The transient circuit comprises: a first feedback circuit, connected to the voltage input terminal and the first reference voltage terminal, and configured to generate a transient voltage signal and an initial transient current signal according to the power supply voltage signal, the synchronization pulse signal and the first reference voltage; The first mirror circuit is connected to the first feedback circuit and is used to mirror the initial transient current signal by K times according to the transient voltage signal to generate the transient current signal.

4. The low voltage detection circuit of the PSI5 protocol synchronization pulse signal according to claim 3, characterized in that: The first feedback circuit comprises: A first resistor, one end of which is connected to the voltage input end; a first operational amplifier, having a non-inverting input terminal connected to the other end of the first resistor and an inverting input terminal connected to the first reference voltage terminal, for making the voltage at the other end of the first resistor follow the first reference voltage, and generating the transient voltage signal according to the power supply voltage signal, the synchronization pulse signal and the first reference voltage; A first transistor, having a gate connected to the output end of the first operational amplifier, a drain connected to the other end of the first resistor, and a source grounded, is used to generate the initial transient current signal according to the transient voltage signal, the power supply voltage signal, the synchronization pulse signal and the first resistor.

5. The low voltage detection circuit of the PSI5 protocol synchronization pulse signal according to claim 4, characterized in that: The first mirror circuit comprises: a second transistor, having a gate connected to the gate of the first transistor, a drain connected to the comparison threshold generating circuit, and a source grounded; The size ratio of the second transistor to the first transistor is K:1, and is used to mirror the initial transient current signal by K times to generate the transient current signal.

6. The low voltage detection circuit of the PSI5 protocol synchronization pulse signal according to claim 1, characterized in that: The comparison threshold generating circuit comprises: a second mirror circuit, connected to the steady-state circuit, for mirroring the average value of the transient current signal by 1 / K times according to the steady-state voltage signal to generate an initial steady-state current signal; a second feedback circuit, connected to the second reference voltage terminal, and generating a reference current signal according to the second reference voltage; a current accumulation circuit, connected to the second mirror circuit, the second feedback circuit and the low-voltage power supply terminal, and used for summing the initial steady-state current signal and the reference current signal to generate an initial comparison threshold current signal; A third mirror circuit, connected to the current accumulation circuit, the transient circuit and the low-voltage power supply terminal, is used to mirror the initial comparison threshold current signal by K times to generate the comparison threshold current signal; When the voltage signal between the output end of the transient circuit and the output end of the third mirror circuit is half of the low-voltage regulated power supply signal, the transient current signal is equal to the comparison threshold current signal, so that the detected synchronization pulse signal is independent of the power supply voltage signal.

7. The low voltage detection circuit of the PSI5 protocol synchronization pulse signal according to claim 6, characterized in that: The second mirror circuit comprises: The third transistor has a gate connected to the steady-state circuit, a drain connected to the current accumulation circuit, and a source connected to the ground, and is used to mirror the average value of the transient current signal by 1 / K times according to the steady-state voltage signal to generate an initial steady-state current signal.

8. The low voltage detection circuit of the PSI5 protocol synchronization pulse signal according to claim 7, characterized in that: The second feedback circuit comprises: A second resistor, one end of which is grounded; A second operational amplifier, having a non-inverting input terminal connected to the second reference voltage terminal and an inverting input terminal connected to the other end of the second resistor, for making the voltage at the other end of the second resistor follow the second reference voltage; A fourth transistor, having a gate connected to the output end of the second operational amplifier, a source connected to the other end of the second resistor, and a drain connected to the current accumulation circuit, is used to generate the reference current signal according to the second reference voltage, the second operational amplifier and the second resistor.

9. The low voltage detection circuit of the PSI5 protocol synchronization pulse signal according to claim 8, characterized in that: The current accumulation circuit comprises a fifth transistor, the drain of the fifth transistor is connected to the drain of the third transistor and the drain of the fourth transistor, the source of the fifth transistor is connected to the low-voltage power supply terminal, and the gate of the fifth transistor is short-circuited with its drain; The third mirror circuit includes a sixth transistor, a gate of the sixth transistor is connected to the gate of the fifth transistor, a source of the sixth transistor is connected to the low-voltage power supply terminal, and a drain of the sixth transistor is connected to the transient circuit; a size ratio of the sixth transistor to the fifth transistor is K:1, and is used to mirror the initial comparison threshold current signal by K times to generate the comparison threshold current signal.

10. The low voltage detection circuit of the PSI5 protocol synchronization pulse signal according to claim 1, characterized in that: It also includes a shaping circuit, which is connected to the transient circuit and the comparison threshold generating circuit, and is used to shape and output the synchronization pulse signal when the transient current signal is equal to the comparison threshold current signal.

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