A low-voltage detection circuit for PSI5 protocol synchronization pulse signals

Abstract

The present invention relates to a low-voltage detection circuit for a PSI5 protocol synchronization pulse signal, which includes a transient circuit, a steady-state circuit, a comparison threshold generation circuit, and a low-voltage power supply terminal that provides a low-voltage regulated power supply signal. The transient circuit generates a transient voltage signal and a transient current signal based on a supply voltage signal, a synchronization pulse signal, and a first reference voltage. The steady-state circuit generates a steady-state voltage signal based on the transient voltage signal. The comparison threshold generation circuit generates a comparison threshold current signal based on the steady-state voltage signal and a second reference voltage. When the voltage between the output terminal of the transient circuit and the output terminal of the comparison threshold generation circuit is half of the low-voltage regulated power supply signal, the transient current signal is equal to the comparison threshold current signal, making the detected synchronization pulse signal independent of the supply voltage signal. In this way, the high accuracy of the low-level detection of the synchronization pulse signal is ensured. Compared with the prior art of high-voltage detection, the circuit structure of the present invention is simple, highly reliable, and low in cost.

Description

Technical Field

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

[0002] The PSI5 (Peripheral Sensor Interface 5) protocol is an open communication protocol applied to automotive sensors. This protocol is well-known for its strong anti-interference characteristics and was initially applied to 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 applicable to new sensor-intensive automotive applications.

[0003] As Figure 1 shown, 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 in parallel to the ECU (Electronic Control Unit); 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 controlled and modulated by the ECU on the power supply voltage signal is as Figure 2 shown, V supply is the normal power supply voltage signal provided by the ECU, and V sync is the synchronous pulse signal issued by the ECU.

[0004] According to the PSI5 protocol, the power supply voltage signal is allowed to vary within a large range, and this large range is between 5V and 16.5V. The synchronous 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 - 5V. Since the power supply voltage signal floats within the range of 5V - 16.5V, the low potential of the synchronous pulse signal is uncertain, that is, the synchronous pulse signal is also floating.

[0005] In the related art, in order to detect a definite synchronous pulse signal, a high-voltage detection circuit is required. However, this circuit structure is relatively complex and has low reliability. Summary of the Invention

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

[0007] The technical solution of the present invention to solve the above technical problems is as follows: A low-voltage detection circuit for a PSI5 protocol synchronization pulse signal, comprising:

[0008] A voltage input terminal for connecting to the PSI5 protocol, where a power supply voltage signal and a synchronization pulse signal are input to the voltage input terminal;

[0009] A first reference voltage terminal for accessing a first reference voltage;

[0010] A transient circuit, connected to the voltage input terminal and the first reference voltage terminal, for generating a transient voltage signal and a transient current signal according to the power supply voltage signal, the synchronization pulse signal, and the first reference voltage;

[0011] A steady-state circuit, connected to the transient circuit, for performing a steady-state process on the transient voltage signal to generate a steady-state voltage signal;

[0012] A second reference voltage terminal for accessing a second reference voltage;

[0013] A comparison threshold generation circuit, connected to the steady-state circuit, the second reference voltage terminal, and the transient circuit, for generating a comparison threshold current signal according to the steady-state voltage signal and the second reference voltage;

[0014] A low-voltage power supply terminal, connected to the comparison threshold generation circuit, for providing a low-voltage regulated power supply signal;

[0015] When the voltage signal between the output terminal of the transient circuit and the output terminal of the comparison threshold generation circuit is one-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.

[0016] Based on the above technical solution, the present invention can be further improved as follows.

[0017] Further, the transient circuit, the steady-state circuit, and the comparison threshold generation circuit all refer to the ground potential.

[0018] Further, the transient circuit includes:

[0019] A first feedback circuit, connected to the voltage input terminal and the first reference voltage terminal, for generating 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;

[0020] A first mirror circuit, connected to the first feedback circuit, for mirroring the initial transient current signal by K times according to the transient voltage signal to generate the transient current signal.

[0021] Further, the first feedback circuit includes:

[0022] A first resistor, one end of which is connected to the voltage input terminal;

[0023] A first operational amplifier, the non-inverting input terminal of which is connected to the other end of the first resistor, and the inverting input terminal of which is 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;

[0024] A first transistor, the gate of which is connected to the output terminal of the first operational amplifier, the drain of which is connected to the other end of the first resistor, and the source of which is grounded, for generating the initial transient current signal according to the transient voltage signal, the power supply voltage signal, the synchronization pulse signal and the first resistor.

[0025] Further, the first mirror circuit includes:

[0026] A second transistor, the gate of which is connected to the gate of the first transistor, the drain of which is connected to the comparison threshold generating circuit, and the source of which is grounded;

[0027] The ratio of the size of the second transistor to that of the first transistor is K:1, for mirroring the initial transient current signal by K times to generate the transient current signal.

[0028] Further, the comparison threshold generating circuit includes:

[0029] 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;

[0030] A second feedback circuit, connected to the second reference voltage terminal, for generating a reference current signal according to the second reference voltage; [[ID= thirty]]

[0031] A current accumulation circuit, connected to the second mirror circuit, the second feedback circuit and the low-voltage power supply terminal, for summing the initial steady-state current signal and the reference current signal to generate an initial comparison threshold current signal;

[0032] 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;

[0033] When the voltage signal between the output terminal of the transient circuit and the output terminal of the third mirror circuit is one-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.

[0034] Further, the second mirror circuit includes:

[0035] A third transistor, with its gate connected to the steady-state circuit, its drain connected to the current accumulation circuit, and its source grounded, is used to mirror the average value of the transient current signal at 1 / K times according to the steady-state voltage signal to generate an initial steady-state current signal.

[0036] Further, the second feedback circuit includes:

[0037] A second resistor, with one end grounded;

[0038] A second operational amplifier, with its non-inverting input terminal connected to the second reference voltage terminal and its inverting input terminal connected to the other end of the second resistor, is used to make the voltage at the other end of the second resistor follow the second reference voltage;

[0039] A fourth transistor, with its gate connected to the output terminal of the second operational amplifier, its source connected to the other end of the second resistor, and its 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.

[0040] Further, the current accumulation circuit includes a fifth transistor. The drain of the fifth transistor is connected to the drains of the third transistor and 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 to its drain;

[0041] The third mirror circuit includes a sixth transistor. The gate of the sixth transistor is connected to the gate of the fifth transistor. The source of the sixth transistor is connected to the low-voltage power supply terminal. The drain of the sixth transistor is connected to the transient circuit; the size ratio of the sixth transistor to the fifth transistor is K:1, and it is used to mirror the initial comparison threshold current signal at K times to generate the comparison threshold current signal.

[0042] Further, it further includes a shaping circuit. The shaping circuit is connected to the transient circuit and the comparison threshold generation 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.

[0043] The beneficial effects of the present invention are as follows: A low-voltage detection circuit for PSI5 protocol synchronous pulse signals provided by the present invention uses a transient circuit and a comparison threshold generation circuit to form a current comparator. Among them, the signal generated by the transient circuit represents the instantaneous values of the power supply voltage signal and the synchronous pulse signal, and the signal generated by the comparison threshold generation circuit represents the steady-state values of the power supply voltage signal and the synchronous pulse signal. At the same time, a low-voltage regulated power supply signal is adopted. Therefore, at the flip point of the current comparator, the detected synchronous pulse signal is independent of the power supply voltage signal, thereby ensuring high accuracy in the low-level detection of the synchronous pulse signal. Moreover, all circuits operate under the low-voltage regulated 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 in cost. Description of the Drawings

[0044] Figure 1 It is a schematic diagram of the bus topology structure based on the PSI5 protocol;

[0045] Figure 2 It is a signal waveform diagram of the synchronous pulse signal modulated by the ECU on the power supply voltage signal;

[0046] Figure 3 It is a structural block diagram of a low-voltage detection circuit for PSI5 protocol synchronous pulse signals provided by the present invention;

[0047] Figure 4 It is a structural block diagram of another low-voltage detection circuit for PSI5 protocol synchronous pulse signals provided by the present invention;

[0048] Figure 5 It is a specific structural block diagram of yet another low-voltage detection circuit for PSI5 protocol synchronous pulse signals provided by the present invention;

[0049] Figure 6 For Figure 5 It is the specific circuit diagram of a low-voltage detection circuit for PSI5 protocol synchronous pulse signals shown;

[0050] Figure 7 It is the waveform diagram of the power supply voltage signal and the synchronous pulse signal in a low-voltage detection circuit for PSI5 protocol synchronous pulse signals of the present invention;

[0051] Figure 8 It is the current waveform diagram flowing through the first transistor and the fifth transistor in a low-voltage detection circuit for PSI5 protocol synchronous pulse signals of the present invention;

[0052] Figure 9 It is the waveform diagram of the comparison result signal in a low-voltage detection circuit for PSI5 protocol synchronous pulse signals of the present invention;

[0053] Figure 10 For Figure 5Specific circuit diagram of another low - voltage detection circuit for PSI5 protocol synchronous pulse signal as shown Detailed implementation mode

[0054] The principles and features of the present invention will be described below in conjunction with the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention

[0055] As Figure 3 shown, a low - voltage detection circuit for PSI5 protocol synchronous pulse signal includes:

[0056] A voltage input terminal 1 for connecting to the PSI5 protocol, and the voltage input terminal 1 inputs a power supply voltage signal V supply and a synchronous pulse signal V sync ;

[0057] A first reference voltage terminal 2 for accessing a first reference voltage V REF1 ;

[0058] A transient circuit 3, connected to the voltage input terminal 1 and the first reference voltage terminal 2, for generating a transient voltage signal V1 and a transient current signal I1 according to the power supply voltage signal V supply , the synchronous pulse signal V sync and the first reference voltage V REF1 ;

[0059] 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;

[0060] A second reference voltage terminal 5 for accessing a second reference voltage V REF2 ;

[0061] A comparison threshold generation circuit 6, connected to the steady - state circuit 4, the second reference voltage terminal 5 and the transient circuit 3, for generating a comparison threshold current signal I2 according to the steady - state voltage signal V2 and the second reference voltage V REF2 ;

[0062] A low - voltage power supply terminal 7, connected to the comparison threshold generation circuit 6, for providing a low - voltage regulated power supply signal VDD;

[0063] When the voltage signal between the output terminal of the transient circuit 3 and the output terminal of the comparison threshold generation circuit 6 is one - half of the low - voltage regulated power supply signal VDD, then the transient current signal I1 is equal to the comparison threshold current signal I2, so that the detected synchronous pulse signal V sync is independent of the power supply voltage signal V supply .

[0064] The present invention uses a transient circuit 3 and a comparison threshold generation circuit 6 to form a current comparator. Among them, the signal generated by the transient circuit 3 represents the instantaneous value of the power supply voltage signal V supply and the synchronization pulse signal V sync The signal generated by the comparison threshold generation circuit 6 represents the steady-state value of the power supply voltage signal V supply and the 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 is independent of the power supply voltage signal V supply Furthermore, the high accuracy of the low-level detection of the synchronization pulse signal V sync is ensured. And all circuits operate 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, highly reliable and low in cost.

[0065] In some embodiments, the transient circuit 3, the steady-state circuit 4, and the comparison threshold generation circuit 6 all refer to the ground potential.

[0066] Specifically, as Figure 4 shown, the transient circuit 3, the steady-state circuit 4, and the comparison threshold generation circuit 6 are all grounded and refer to the ground potential. The advantage of this design is that there is no floating reference voltage in the circuit, thereby reducing interference and achieving the purpose of being insensitive to interference.

[0067] In some embodiments, as Figure 5 shown, the transient circuit 3 includes:

[0068] A first feedback circuit 31, connected to the voltage input terminal 1 and the first reference voltage terminal 2, for generating a transient voltage signal V1 and an initial transient current signal I1' according to the power supply voltage signal V supply the synchronization pulse signal V sync and the first reference voltage V REF1 ;

[0069] A first mirror circuit 32, connected to the first feedback circuit 31, 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.

[0070] Specifically, both the transient voltage signal V1 and the initial transient current signal I1' are based on the power supply voltage signal V supply and the synchronization pulse signal V syncis generated. Therefore, both the transient voltage signal V1 and the initial transient current signal I1' generated by the first feedback circuit 31 characterize the supply voltage signal V supply and the synchronization pulse signal V sync instantaneous values. The first mirror circuit 32 can easily and accurately replicate the initial transient current signal I1' using the current mirror principle, and thus the obtained transient current signal I1 also characterizes the supply voltage signal V supply and the synchronization pulse signal V sync instantaneous values.

[0071] In some embodiments, as Figure 5 shown, the comparison threshold generating circuit 6 includes:

[0072] 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'';

[0073] A second feedback circuit 62, connected to the second reference voltage terminal 5, generating a reference current signal I REF2 according to the second reference voltage V REF ;

[0074] A current accumulation circuit 63, connected to the second mirror circuit 61, the second feedback circuit 62 and the low-voltage power supply terminal 7, for summing the initial steady-state current signal I1'' and the reference current signal I REF to generate an initial comparison threshold current signal I2';

[0075] 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;

[0076] When the voltage signal between the output terminal of the transient circuit 3 and the output terminal of the third mirror circuit 64 is one-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 is independent of the supply voltage signal V supply .

[0077] 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 characterize the steady-state value of the transient voltage signal V1. Also, because the transient voltage signal V1 is used to characterize the supply voltage signal V supply and the synchronization pulse signal V syncThe instantaneous value, so the steady-state voltage signal V2 can be used to characterize the power supply voltage signal V supply and the synchronization pulse signal V sync of the steady-state value.

[0078] 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 a fixed reference signal to obtain a comparison result. The real-time signal here is the transient current signal I1 that characterizes the instantaneous value of the power supply voltage signal V supply and the synchronization pulse signal V sync . To obtain the fixed reference signal here, the present invention uses the second feedback circuit 62 to generate a reference current signal I REF ; however, the power supply voltage signal V supply is floating. To avoid the influence of the floating power supply voltage signal V supply on the synchronization pulse signal V sync , the present invention superimposes the reference current signal I REF with the steady-state voltage signal V2 that characterizes the steady-state value of the power supply voltage signal V supply and the synchronization pulse signal V sync to obtain an initial comparison threshold current signal I2'. The initial comparison threshold current signal I2' also characterizes the steady-state value of the power supply voltage signal V supply and the synchronization pulse signal V sync of the steady-state value.

[0079] To ensure the comparison accuracy of the current comparator, the two signals to be compared need to have the same amplification factor. Since the transient current signal I1 obtained in the transient circuit 3 is a K-fold mirror image of the initial transient current signal I1' that characterizes the instantaneous value of the power supply voltage signal V supply and the synchronization pulse signal V sync , it is also necessary to perform the same multiple of mirror image replication on the initial comparison threshold current signal I2' that characterizes the steady-state value of the power supply voltage signal V supply and the synchronization pulse signal V sync 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 correspondingly obtain the transient current signal I1 and the comparison threshold current signal I2, and further compares the two, so as to improve the stability and reliability of the comparison result.

[0080] In some embodiments, as Figure 6 shown, the first feedback circuit 31 includes:

[0081] The first resistor R1, one end of which is connected to the voltage input terminal 1;

[0082] The first operational amplifier A1, the non-inverting input terminal is connected to the other end of the first resistor R1, and the inverting input terminal is connected to the first reference voltage terminal 2, for making the voltage at the other end of the first resistor R1 follow the first reference voltage V REF1 , and generating the transient voltage signal V1 according to the power supply voltage signal V supply , the synchronization pulse signal V sync and the first reference voltage V REF1 ;

[0083] The first transistor M1, the gate is connected to the output terminal of the first operational amplifier A1, the drain is connected to the other end of the first resistor R1, and the source is grounded to GND, for generating the initial transient current signal I1' according to the transient voltage signal V1, the power supply voltage signal V supply , the synchronization pulse signal V sync and the first resistor R1.

[0084] Specifically, one end of the first resistor R1 is connected to the voltage input terminal 1, and the waveforms of the power supply voltage signal V supply and the synchronization pulse signal V sync input thereto are as Figure 7 shown. The ECU modulates the synchronization pulse signal Vsync on the power supply voltage signal V supply to form the composite signal V IN , so V IN = V supply + V sync . The composite signal VIN can be obtained from the sensor power supply terminal or from the ECU power supply pulse signal output terminal. Therefore, one end of the first resistor R1 is connected to the sensor power supply terminal or the ECU power supply pulse signal output terminal.

[0085] The first resistor R1, the first operational amplifier A1 and the first transistor M1 form the first feedback circuit; the signal output from the output terminal of the first operational amplifier A1 depends on the transient value of the composite signal VIN. Therefore, the transient voltage signal V1 represents the transient value of the composite 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 , the voltage at the other end of the first resistor R1 is equal to the first reference voltage V REF1 , that is, Figure 6 the voltage at point A in REF1 is equal to the first reference voltage V REF1 is selected to be lower than the power supply voltage signal V supplyis low, 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.

[0086] The transient voltage signal V1 output from the output terminal of the first operational amplifier A1 is connected to the gate of the first transistor M1 to provide an opening 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 M1 flowing through the first transistor M1 R1 is equal to the current I M1 flowing through the first resistor R1, that is, I R1 = I R1 . Therefore, the initial transient current signal I1' generated by the first feedback circuit 31 is the current I M1 flowing through the first resistor R1, M1 which is also the current I R1 flowing through the first transistor M1; thus, I1' = I IN = I REF1 = (V supply – V sync ) / R1 = (V REF1 + V M1 – V Figure 8 ) / R1. Among them, the waveform of the current I

[0087] flowing through the first transistor M1

[0088] In some embodiments, as Figure 6 shown, the first mirror circuit 32 includes:

[0089] A second transistor M2, with its gate connected to the gate of the first transistor M1, its drain connected to the comparison threshold generation circuit 6, and its source grounded to GND;

[0090] The size ratio of the second transistor M2 to the first transistor M1 is K:1, and it 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.

[0091] Specifically, the second transistor M2 and the first transistor M1 in the first feedback circuit 31 form a current mirror, and the magnitudes of the currents flowing through them are 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) to enable the second transistor M2 to mirror the current I flowing through the first transistor M1 by K times. M1 .

[0092] 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’.

[0093] The current I flowing through the second transistor M2 M2 depends on its gate voltage, and the gate of the second transistor M2 is connected to the output terminal of the first operational amplifier A1 to output the transient voltage signal V1, and the transient voltage signal V1 depends on the transient value of the composite signal V IN . Therefore, the transient current signal I1 characterizes the transient value of the composite signal V IN .

[0094] The first mirror circuit 12 only includes one second transistor M2, and its circuit structure is simple, easy to implement and has low cost; at the same time, the second transistor M2 operates under a low-voltage power supply and has good reliability.

[0095] In some embodiments, as Figure 6 shown, the second mirror circuit 61 includes:

[0096] A third transistor M3, with its gate connected to the steady-state circuit 4, its drain connected to the current accumulation circuit 63, and its source grounded to GND, 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’’.

[0097] 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 magnitudes of the currents flowing through them are proportional to their sizes; therefore, the size ratio of the second transistor M2 to the third transistor M3 can be set to K:1 to enable the third transistor M3 to mirror the current I flowing through the second transistor M2 by 1 / K times. M2The gate of the third transistor M3 is connected to the steady-state circuit 4. Therefore, the gate voltage of the third transistor M3 is the steady-state voltage signal V2. The steady-state voltage signal V2 drives the third transistor M3 to operate. Therefore, the current I flowing through the third transistor M3 M3 is equal to 1 / K times of I M2 's steady-state value. And I M2 = K * I M1 , so the current I flowing through the third transistor M3 M3 is equal to the steady-state value of the current I flowing through the first transistor M1 M1 , that is, 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 for calculating the average value. Since the synchronous pulse signal V sync is just a narrow pulse in terms of time and its proportion in the mean value is small, when calculating the steady-state value of the current I M1 flowing through the first transistor M1, the synchronous pulse signal V sync can be ignored. So I M3 ≈ (V supply – V REF1 ) / R1.

[0098] The second mirror circuit 61 only includes a third transistor M3, and its circuit structure is simple, easy to implement and has low cost; at the same time, the third transistor M3 operates under a low-voltage power supply and has good reliability.

[0099] In some embodiments, as Figure 6 shown, the second feedback circuit 62 includes:

[0100] A second resistor R2, one end of which is grounded to GND;

[0101] A second operational amplifier A2, the non-inverting input terminal of which is connected to the second reference voltage terminal 5, and the inverting input terminal is connected to the other end of the second resistor R2, for making the voltage at the other end of the second resistor R2 follow the second reference voltage V REF2 ;

[0102] A fourth transistor M4, the gate of which is connected to the output terminal of the second operational amplifier A2, the source of which is connected to the other end of the second resistor R2, and the drain of which is connected to the current accumulation circuit 63, for generating the reference current signal I REF2 according to the second reference voltage V REF。

[0103] Specifically, in the second feedback circuit 62, the signal output from the output terminal of the second operational amplifier A2 (i.e., the voltage signal V3 in Figure 6 ) 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 non-inverting 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, and the non-inverting input terminal of the second operational amplifier A2 is connected to the second reference voltage V REF2 , the voltage at the other end of the second resistor R2 is equal to the second reference voltage V REF2 , that is, the voltage at point B in Figure 6 is equal to the second reference voltage V REF2 . Therefore, the current I R2 flowing through the second resistor R2 can be calculated, that is, I R2 = V REF2 / R2.

[0104] The voltage signal V3 output from the output terminal of the second operational amplifier A2 is connected to the gate of the fourth transistor M4 to provide an opening 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 M4 flowing through the fourth transistor M4 is equal to the current I R2 flowing through the second resistor R2, that is, I M4 = I R2 . Therefore, the reference current signal I REF generated by the second feedback circuit 62 is the current I R2 flowing through the second resistor R2, that is, the current I M4 flowing through the fourth transistor M4, that is, I REF = I M4 = I R2 = V REF2 / R2.

[0105] The second feedback circuit 62 operates under a low-voltage power supply. Therefore, it can be implemented by using several simple devices such as the second resistor R2, the second operational amplifier A2, and the fourth transistor M4. Thus, its circuit structure is simple, easy to implement, and has low cost; at the same time, the fourth transistor M4 in the second feedback circuit 62 operates under a low-voltage power supply, and its reliability is good.

[0106] In some embodiments, such as Figure 6As shown, the current accumulation circuit 63 includes a fifth transistor M5. The drain of the fifth transistor M5 is connected to the drains of the third transistor M3 and the fourth transistor M4. The source of the fifth transistor M5 is connected to the low-voltage power supply terminal 7. The gate of the fifth transistor M5 is shorted to its drain.

[0107] The third mirror circuit 64 includes a sixth transistor M6. The gate of the sixth transistor M6 is connected to the gate of the fifth transistor M5. The source of the sixth transistor M6 is connected to the low-voltage power supply terminal 7. The 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, which is used to mirror the initial comparison threshold current signal I2' by K times to generate the comparison threshold current signal I2.

[0108] Specifically, the low-voltage regulated signal VDD input by the low-voltage power supply terminal 7 can be provided inside the sensor. The fifth transistor M5 is connected to both the third transistor M3 and the fourth transistor M4 at the same time. It is equivalent to the fifth transistor M5 being connected in series with the second mirror circuit 61 and also in series with the second feedback circuit 62. Therefore, the current I flowing through the fifth transistor M5 M5 is equal to the sum of the steady-state current signal I1'' in the second mirror circuit 61 and the reference current signal I in the second feedback circuit 62, that is, I REF 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 waveform of the current I flowing through the fifth transistor M5 M5 can be seen in the dashed line shown in Figure 8 .

[0109] The current accumulation circuit 63 realizes the current accumulation of two branches through the fifth transistor M5. Its circuit structure is simple, easy to implement and has low cost. At the same time, the fifth transistor M5 works under a low-voltage power supply and has good reliability.

[0110] ​The sixth transistor M6 in the third mirror circuit 64 and the fifth transistor M5 in the current accumulation circuit 63 form a current mirror, and the magnitudes of the currents flowing through them are 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 is 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].

[0111] The comparison threshold current signal I2 is the current I flowing through the sixth transistor M6 M6 , which serves as a comparison threshold for detecting the synchronization pulse signal V sync ; 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 steady-state value of the supply voltage signal V supply and the reference voltage V REF . As Figure 6 shown, the third mirror circuit 64 and the first mirror circuit 32 are connected at point C to form a current comparator, and the potential of point C is determined by the magnitudes of the currents in the third mirror circuit 64 and the first mirror circuit 32. Specifically, when the potential of point C is exactly in the middle between VDD and GND (i.e., 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 M1 increases, the current of I M2 increases accordingly, and the potential of point C drops, and vice versa, so the waveform of the comparison result signal Rx as shown in Figure 9 can be obtained. The comparison result signal Rx is the potential of point C. When the synchronization pulse signal V supply is superimposed on the supply voltage signal V syncWhen the potential at point C flips, the waveform of the comparison result signal Rx is thus the same as that of the synchronization pulse signal V sync 's waveform.

[0112] At the flip point (comparison threshold) of the current comparator, according to I M6 = K * I M5 , I M2 = K * I M1 , and I1 = I2 (i.e., I M6 = I M2 ), it can be obtained that: V sync ≈ V REF2 * R1 / R2; Therefore, it can be seen that the comparison threshold is independent of the power supply voltage signal V supply and the first reference voltage V REF1 , and is only related to the ratio of the first resistor R1 to the second resistor R2 and the second reference voltage V REF2 . Thus, the accuracy of the detected synchronization pulse signal V supply is relatively high.

[0113] In some embodiments, as Figure 6 shown, the steady-state circuit 4 is specifically an RC filter, which includes:

[0114] Filtering resistor R FLT , one end is connected to the gate of the second transistor M2, and the other end is connected to the gate of the third transistor M3;

[0115] Filtering capacitor C FLT , one end is connected to the other end of the filtering resistor R FLT , and the other end is grounded.

[0116] The RC filter is used to perform steady-state processing on the transient voltage signal V1 (i.e., to achieve averaging processing through filtering); using an RC filter as the steady-state circuit 4, its circuit structure is simple, easy to implement, and low in cost.

[0117] In some embodiments, as Figure 5 shown, the low-voltage detection circuit of the present invention further includes a shaping circuit 8. The shaping circuit 8 is connected to the transient circuit 3 and the comparison threshold generation circuit 6, and is used to shape and output the synchronization pulse signal V sync when the transient current signal I1 is equal to the comparison threshold current signal I2.

[0118] Specifically, as Figure 10 shown, the shaping circuit 8 is specifically a Schmitt trigger X0. The Schmitt trigger X0 shapes the voltage at point C to avoid problems such as distortion and noise interference, thereby obtaining a more accurate and stable signal, and further making the shaped comparison result signal Rx and the synchronization pulse signal Vsync Basically remain the same.

[0119] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A low-voltage detection circuit for PSI5 protocol synchronization pulse signals, characterized in that, Comprising: A voltage input terminal for connecting to the PSI5 protocol, where the voltage input terminal inputs a power supply voltage signal and a synchronization pulse signal; wherein, the synchronization pulse signal is modulated on the power supply voltage signal to form a composite signal; A first reference voltage terminal for accessing a first reference voltage; A transient circuit, comprising: A first feedback circuit, connected to the voltage input terminal and the first reference voltage terminal, for generating 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; A first mirror circuit, connected to the first feedback circuit, for mirroring the initial transient current signal by K times according to the transient voltage signal to generate the transient current signal; Wherein, the transient current signal characterizes the transient value of the composite signal; 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 for accessing a second reference voltage; A low-voltage power supply terminal for providing a low-voltage regulated power supply signal; A comparison threshold generation circuit, comprising: 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, for 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, 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 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; Wherein, the comparison threshold current signal characterizes the steady-state value of the composite signal; The third mirror circuit and the first mirror circuit are connected to form a current comparator; When the potential at the connection point of the third mirror circuit and the first mirror circuit is one-half of the low-voltage regulated power supply signal, then the transient current signal is equal to the comparison threshold current signal, so that the synchronization pulse signal is independent of the power supply voltage signal.

2. The low-voltage detection circuit for the PSI5 protocol synchronous pulse signal according to claim 1, wherein The transient circuit, the steady-state circuit, and the comparison threshold generation circuit are all referenced to the ground potential.

3. The low-voltage detection circuit for the PSI5 protocol synchronous pulse signal according to claim 1, characterized in that, The first feedback circuit includes: A first resistor, one end of which is connected to the voltage input terminal; A first operational amplifier, the non-inverting input terminal of which is connected to the other end of the first resistor, and the inverting input terminal of which is 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, the gate of which is connected to the output terminal of the first operational amplifier, the drain of which is connected to the other end of the first resistor, and the source of which is grounded, for generating the initial transient current signal according to the transient voltage signal, the power supply voltage signal, the synchronization pulse signal, and the first resistor.

4. The low-voltage detection circuit for the PSI5 protocol synchronization pulse signal according to claim 3, wherein The first mirror circuit includes: A second transistor, with its gate connected to the gate of the first transistor, its drain connected to the comparison threshold generation circuit, and its source grounded; The size ratio of the second transistor to the first transistor is K:1, and it is used to mirror the initial transient current signal by K times to generate the transient current signal.

5. The low-voltage detection circuit for the PSI5 protocol synchronization pulse signal according to claim 1, characterized in that, The second mirror circuit includes: A third transistor, with its gate connected to the steady-state circuit, its drain connected to the current accumulation circuit, and its source grounded. It 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.

6. The low-voltage detection circuit for the PSI5 protocol synchronization pulse signal according to claim 5, characterized in that, The second feedback circuit includes: A second resistor, with one end grounded; A second operational amplifier, with its non-inverting input terminal connected to the second reference voltage terminal and its inverting input terminal connected to the other end of the second resistor, and it is used to make the voltage at the other end of the second resistor follow the second reference voltage; A fourth transistor, with its gate connected to the output terminal of the second operational amplifier, its source connected to the other end of the second resistor, and its drain connected to the current accumulation circuit, and it is used to generate the reference current signal according to the second reference voltage, the second operational amplifier and the second resistor.

7. The low-voltage detection circuit for the PSI5 protocol synchronous pulse signal according to claim 6, characterized in that, The current accumulation circuit includes a fifth transistor. The drain of the fifth transistor is connected to the drains of the third transistor and 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 to its drain; The third mirror circuit includes a sixth transistor. The gate of the sixth transistor is connected to the gate of the fifth transistor. The source of the sixth transistor is connected to the low-voltage power supply terminal. The drain of the sixth transistor is connected to the transient circuit. The size ratio of the sixth transistor to the fifth transistor is K:1, and it is used to mirror the initial comparison threshold current signal by K times to generate the comparison threshold current signal.

8. The low-voltage detection circuit for the PSI5 protocol synchronization pulse signal according to claim 1, characterized in that, It further includes a shaping circuit. The shaping circuit is connected to the transient circuit and the comparison threshold generation circuit, and it 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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