Low-response-delay zero-voltage detection and over-current short-circuit detection circuit
By introducing pull-up circuits and voltage comparator circuits into the gate driver and using resistors of different resistance values to control the switching state, the problem of high response delay in existing voltage detection circuits is solved, achieving fast zero-voltage and overcurrent short-circuit detection, which is suitable for devices such as silicon carbide field-effect transistors.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-14
- Publication Date
- 2026-04-03
AI Technical Summary
The voltage detection circuit in existing gate drivers has a high response delay, and the introduction of filter capacitors increases the complexity of circuit design and response delay, making it difficult to achieve fast zero-voltage and overcurrent short-circuit detection in devices such as silicon carbide field-effect transistors.
A detection circuit is adopted, which includes a pull-up power supply, a pull-up circuit, a voltage comparator circuit and an isolation diode. The voltage comparator circuit controls the on/off state of the switch. Resistors with different resistance values are used to maintain low impedance during the detection stage to improve anti-interference capability, and switch to high impedance state after detection to reduce static loss.
It significantly reduces the response delay of the voltage detection circuit, improves anti-interference capability and the reliability of detection results, reduces static losses, and is suitable for integrated design.
Smart Images
Figure CN121784356A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of detection circuit technology for power devices, specifically to a zero-voltage detection and overcurrent / short-circuit detection circuit with low response delay. Background Technology
[0002] In recent years, with the development of power transistors, especially silicon carbide field-effect transistors (MOSFETs), the on-resistance of electronic devices has been continuously reduced, resulting in better power conversion efficiency. On the one hand, switching losses and conduction losses are often mutually exclusive in device design. Therefore, zero-voltage switching (ZVS) is often used in circuit applications to reduce switching losses. In certain special circuits, such as auxiliary resonant commutated pole inverters (ARCP-Inverters), when the inductive reactance of the auxiliary resonant coil is low, the time window for the switching devices in the half-bridge circuit to achieve zero-voltage conduction becomes significantly smaller. Therefore, in some special designs, the gate driver needs to detect the voltage across the switching device in real time and quickly determine its voltage state, controlling its gate to turn on the channel. Simultaneously, due to the wide bandgap of semiconductors, the freewheeling voltage drop of the body diode or reverse path is significantly higher. To reduce the excessive conduction losses generated by this, the gate of the switching device must be controlled to turn on the channel promptly after the terminal voltage drops to zero. On the other hand, as switching devices strive for lower on-resistance, their chip area and cell density are constantly increasing, resulting in higher short-circuit current and shorter short-circuit capability. This necessitates that the gate driver detects the fault as quickly as possible after an overcurrent or short circuit occurs and shuts down the switching device.
[0003] In existing voltage detection circuits integrated into gate drivers, such as desaturation detection (DESAT) circuits, a filter capacitor needs to be connected to its input. The specifications of this filter capacitor need to be matched according to the junction capacitance of the selected isolation diode and the interference conditions of the application environment, making circuit design tricky; and the introduction of this filter capacitor inevitably increases the response delay of the circuit.
[0004] Therefore, it is necessary to design a new detection circuit to solve the above problems. Summary of the Invention
[0005] The purpose of this invention is to provide a zero-voltage detection and overcurrent / short-circuit detection circuit with low response delay, in order to solve the technical problems existing in the background art.
[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:
[0007] A low-response-delay zero-voltage detection and overcurrent / short-circuit detection circuit is used for rapid detection of the terminal voltage of switching devices. The state;
[0008] The low-response-delay zero-voltage detection and overcurrent / short-circuit detection circuit includes a pull-up power supply U1, a pull-up circuit, a voltage comparator circuit, a threshold reference source, and an isolation diode D.
[0009] The pull-up circuit includes a first pull-up resistor R1 and a second pull-up resistor R connected in parallel. H Furthermore, a switch S1 is connected in series in the branch where the first pull-up resistor R1 is located, and the on / off state of the switch S1 is controlled by the voltage comparison circuit.
[0010] One end of the main circuit of the pull-up circuit is connected to the positive terminal of the pull-up power supply U1, and the other end is connected to the anode of the isolation diode D;
[0011] The cathode of the isolation diode D is connected to one end of the switching device, and the other end of the switching device is connected to the negative terminal of the pull-up power supply U1.
[0012] The first input terminal of the voltage comparison circuit is connected to the threshold reference source to obtain a reference voltage. The second input terminal is connected between the pull-up circuit and the isolation diode D to obtain the detection voltage corresponding to the terminal voltage of the switching device. ;
[0013] The output terminal of the voltage comparison circuit is connected to the control terminal of the switch S1;
[0014] The voltage comparison circuit is based on and The comparison result is used to output a corresponding signal to the control terminal of the switch S1, and this signal is used as the output signal of the low response delay zero voltage detection and overcurrent short circuit detection circuit, that is, the zero voltage detection signal ZVD-S is output to the outside.
[0015] In some embodiments, when the voltage comparison circuit detects the terminal voltage of the switching device... When it is in a high state, that is When the switch S1 is turned on, the output signal controls the switch to conduct and outputs the terminal voltage corresponding to the switching device. The zero-voltage detection signal ZVD-S is in a high state; when the voltage comparator circuit detects the terminal voltage of the switching device... When it is in a low state, that is When the switch S1 is open, the output signal controls the switch to open and outputs the terminal voltage corresponding to the switching device. The zero-voltage detection signal ZVD-S is for the low-state condition.
[0016] In some embodiments, the second pull-up resistor R H The resistance value is greater than the resistance value of the first pull-up resistor R1.
[0017] In some embodiments, the switch S1 is a field-effect transistor, and the switch S1 is configured with a corresponding driving circuit, which controls its gate according to the output signal of the voltage comparison circuit.
[0018] In some embodiments, in the pull-up circuit, the first pull-up resistor R1 and the switch S1 are integrated into a single device, that is, the on-resistance of the switch S1 is R1.
[0019] In some embodiments, a first delay circuit is provided between the output terminal of the voltage comparison circuit and the control terminal of the switch S1, so that the conduction operation of the switch S1 is executed in real time, while its turn-off operation is executed with a delay.
[0020] In some embodiments, a second delay circuit is further provided between the output terminal of the voltage comparison circuit and the output terminal corresponding to the zero voltage detection signal ZVD-S, so that the terminal voltage of the corresponding switching device is... The zero-voltage detection signal ZVD-S when changing from a high state to a low state is output in real time, while the zero-voltage detection signal ZVD-S when changing from a low state to a high state is output with a delay.
[0021] In some embodiments, a capacitor C1 is connected in parallel with the first pull-up resistor R1 to further reduce the transient impedance of the pull-up circuit when the switch S1 is turned on.
[0022] In some embodiments, the switching device is configured with a gate driver, which is used to control the gate voltage of the switching device, thereby controlling the on / off state of the switching device;
[0023] The zero-voltage detection signal ZVD-S output by the low-response-delay zero-voltage detection and overcurrent / short-circuit detection circuit is also input to the gate driver. When the terminal voltage of the switching device... When the state is low, the switching device is automatically turned on when it needs to be turned on;
[0024] When the switching device is in the ON state, and the terminal voltage of the switching device... The switching device is automatically turned off when it goes into a high state.
[0025] In some embodiments, the output signal of the voltage comparison circuit is also input to a threshold reference source, causing the reference voltage output by the threshold reference source to be... It can be set according to the comparison result of the voltage comparison circuit.
[0026] Compared with existing technologies, the low-response-delay zero-voltage detection and overcurrent / short-circuit detection circuit provided by this invention utilizes the output state of the voltage comparison circuit built into the detection circuit to connect resistors of different resistance values into the pull-up circuit. This allows the pull-up circuit to maintain a low impedance during the detection phase, thereby improving anti-interference capability while achieving low response delay performance, and switches to a high impedance state after detection to reduce static losses. This offers the following advantages:
[0027] 1) The filter capacitor located at the input of the voltage comparator circuit can be directly eliminated or only a very small capacitance specification can be used, thereby significantly reducing the response delay of the voltage detection circuit and providing voltage state detection capability with the same low delay performance at both the rising and falling edges of the voltage at the switching device.
[0028] 2) Since the interference generated by the junction capacitance of the isolation diode during charging and discharging can be suppressed by adjusting the resistance value in the pull-up circuit, it can be compatible with a wide range of isolation diodes, thereby reducing the difficulty of device selection and improving device compatibility.
[0029] 3) By automatically switching the pull-up circuit to a low-impedance state when the terminal voltage of the switching device is in the measured high state, the anti-interference capability of the voltage detection circuit is improved, and the reliability of the detection results is enhanced. Conversely, by automatically switching the pull-up resistor to a high-impedance state when the terminal voltage of the switching device is in the low state, the static loss of the voltage detection circuit is reduced.
[0030] 4) It eliminates the need for large-capacity filter capacitors found in traditional circuits (which are typically around several nF in conventional circuits). The entire detection circuit consists of transistors (such as field-effect transistors as switches S1, comparators, etc.) and resistors, making it more compatible with integrated design. Attached Figure Description
[0031] To more clearly illustrate the technical solutions in this embodiment, the accompanying drawings used in the description of the embodiment will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0032] Figure 1 This is a schematic diagram of the low-response-delay zero-voltage detection and overcurrent-short-circuit detection circuit in the first embodiment.
[0033] Figure 2 This is a graph showing the different states of the circuit during the on and off processes of the switching device in the first embodiment;
[0034] Figure 3 The graph shows the different states of the circuit during the automatic shutdown process of the zero-voltage detection signal in the first embodiment.
[0035] Figure 4 This is a schematic diagram of the low-response-delay zero-voltage detection and overcurrent-short-circuit detection circuit in the second embodiment;
[0036] Figure 5 This is a schematic diagram of the low-response-delay zero-voltage detection and overcurrent-short-circuit detection circuit in the third embodiment;
[0037] Figure 6 This is a graph showing the different states of the circuit during the on and off processes of the switching device in the third embodiment;
[0038] Figure 7 This is a schematic diagram of the first delay circuit;
[0039] Figure 8 This is a schematic diagram of another type of first delay circuit;
[0040] Figure 9 This is a schematic diagram of the low-response-delay zero-voltage detection and overcurrent-short-circuit detection circuit in the fourth embodiment.
[0041] Figure 10 This is a graph showing the different states of the circuit during the on and off processes of the switching device in the fourth embodiment;
[0042] Figure 11 This is a schematic diagram of the second delay circuit;
[0043] Figure 12 This is a schematic diagram of the low-response-delay zero-voltage detection and overcurrent / short-circuit detection circuit in the fifth embodiment. Detailed Implementation
[0044] To make the technical means, creative features, objectives and effects of this invention easier to understand, the following description, in conjunction with the accompanying drawings and specific embodiments, further explains how this invention is implemented.
[0045] In the first embodiment, refer to Figure 1 As shown, this invention provides a low-response-delay zero-voltage detection and overcurrent / short-circuit detection circuit (hereinafter referred to as detection circuit 1) for quickly detecting the terminal voltage of switching devices. The state.
[0046] The detection circuit 1 includes a pull-up power supply U1, a pull-up circuit 2, a voltage comparison circuit 3, a threshold reference source 4, and an isolation diode D; the pull-up circuit 2 includes a first pull-up resistor R1 and a second pull-up resistor R connected in parallel. HFurthermore, a switch S1 is connected in series in the branch containing the first pull-up resistor R1, and the on / off state of the switch S1 is controlled by the voltage comparator circuit 3; one end of the main circuit of the pull-up circuit 2 is connected to the positive terminal of the pull-up power supply U1, and the other end is connected to the anode of the isolation diode D; the cathode of the isolation diode D is connected to one end of the switching device, and the other end of the switching device is connected to the negative terminal of the pull-up power supply U1; the first input terminal of the voltage comparator circuit 3 is connected to the threshold reference source 4 to obtain the reference voltage. The second input terminal is connected between the pull-up circuit 2 and the isolation diode D to obtain the detection voltage corresponding to the terminal voltage of the switching device. The output terminal of voltage comparator circuit 3 is connected to the control terminal of switch S1; voltage comparator circuit 3 according to... and The comparison result is used to output a corresponding signal to the control terminal of switch S1, and this signal is used as the output signal of detection circuit 1, that is, the zero voltage detection signal ZVD-S is output to the outside.
[0047] Furthermore, when the voltage comparator circuit 3 detects the terminal voltage of the switching device... When it is in a high state, that is When the output signal turns on switch S1, it outputs the corresponding terminal voltage of the switching device. The zero-voltage detection signal ZVD-S is in a high state, which is logic "0" in this embodiment; when the voltage comparator circuit 3 detects the terminal voltage of the switching device... When it is in a low state, that is When the output signal controls switch S1 to open, it outputs the terminal voltage corresponding to the switching device. The zero-voltage detection signal ZVD-S is in a low state, and in this embodiment it is logic "1".
[0048] Preferably, the second pull-up resistor R H The resistance value is greater than the resistance value of the first pull-up resistor R1. The second pull-up resistor R... H The resistance value can be several times to thousands of times that of the first pull-up resistor R1, meaning the first pull-up resistor R1 is a low-impedance design, and in specific designs it can be several ohms to tens of ohms, for example: 5Ω~20Ω; the second pull-up resistor R H Designed for high impedance, the impedance can be several thousand ohms in specific designs, for example: 1kΩ~5kΩ.
[0049] In this embodiment, two configurable parallel pull-up resistors are provided in pull-up circuit 2, and their resistance values differ significantly. The second pull-up resistor R... HThe first pull-up resistor R1 has a higher resistance value and is directly connected to the pull-up power supply U1 and the isolation diode D, providing a smaller base pull-up current. The first pull-up resistor R1 has a lower resistance value and is connected between the pull-up power supply U1 and the isolation diode D through the corresponding switch S1; its connection state is determined by the comparison result of the voltage comparison circuit 3; when it is connected, it can reduce the impedance of the pull-up circuit 2, thereby improving the anti-interference performance of the entire detection circuit 1.
[0050] Additionally, it is understood that in this application, "first pull-up resistor R1" and "second pull-up resistor R" are different. H The focus is on the resistance value, not the number of resistors. In other embodiments, the pull-up circuit 2 may have more than two resistors; instead, each branch may use a combination of several resistors, such that one branch is controlled by switch S1 and has a resistance of R1, while another branch has a resistance of R... H Alternatively, the first pull-up resistor R1 and switch S1 can be integrated into a single device without a separate resistor entity; that is, the on-resistance of switch S1 is R1. These embodiments are similar to... Figure 1 The pull-up circuit 2 in the above is essentially the same.
[0051] Due to the function of the isolation diode D, when the terminal voltage of the switching device... Higher than the pull-up power supply voltage At that time, the detection voltage is input to voltage comparator circuit 3. Always for Due to the reference voltage Below At this time, voltage comparator circuit 3 outputs the terminal voltage of the corresponding switching device. In this embodiment, the zero-voltage detection signal ZVD-S output by detection circuit 1 is logic "0" as a high-state signal. Simultaneously, switch S1 is turned on by voltage comparator circuit 3, at which point the total pull-up resistor... It consists of two resistors connected in parallel, since R1 is much smaller than R H , can be simplified At this time, pull-up circuit 2 is in a low impedance state.
[0052] During the switching process, due to the junction capacitance of the isolation diode D... The voltage fluctuations generated across the pull-up resistor by the injected current during charging and discharging. for:
[0053]
[0054] In this case, the advantage of the solution provided by the present invention is that it can be achieved by selecting a low-resistance pull-up resistor. This causes voltage fluctuations It is controlled within a range far from the comparison threshold of voltage comparator circuit 3 to meet the following anti-interference requirements:
[0055]
[0056] Using voltage change rate, which is common in practical applications For example, when using junction capacitance When using a silicon carbide Schottky diode with a capacitance of approximately 10pF, the injected current due to its charging and discharging will reach 200mA. In conventional solutions, this current needs to be absorbed by a filter capacitor. However, in this invention, because the pull-up circuit 2 is in a low-impedance state at this time, voltage fluctuations are generated across it. It can be suppressed to within a few volts with the first pull-up resistor. For example, voltage fluctuations Only 2V. This improves the anti-interference capability during zero-voltage detection as described in this invention.
[0057] When the terminal voltage of the switching device Less than the pull-up power supply voltage When the isolation diode D is turned on, at this time Voltage comparison circuit 3 begins actual comparison and .when Below At that time, voltage comparator circuit 3 outputs the terminal voltage of the corresponding switching device. This is a low-state signal. At this time, switch S1 is turned off by voltage comparator circuit 3, providing a low-resistance first pull-up resistor with high anti-interference capability. The pull-up circuit is disconnected, and the total pull-up resistance becomes R. H In this embodiment, the detection circuit 1 outputs a zero-voltage detection signal ZVD-S of logic "1".
[0058] When the switching device (MOSFET) is in the ON state, the pull-up power supply U1 is actually short-circuited by the pull-up circuit 2 through the switching device. The advantage obtained by the above control method is that the static pull-up loss generated by the low-resistance line in the pull-up circuit 2 can be significantly reduced because the low-resistance line in the pull-up circuit 2 is disconnected.
[0059] It is understood that the detection circuit 1 can be applied to the gate drive circuit of various power circuits. In this embodiment, it is applied to a circuit that includes a switching device (MOSFET) and a gate driver 5. The switching device (MOSFET) and the gate driver 5 are prior art. The gate driver 5 is used to control the gate voltage of the switching device, thereby controlling the on / off state of the switching device.
[0060] The zero-voltage detection signal ZVD-S output by detection circuit 1 is also input to gate driver 5. When the terminal voltage of the switching device... When the switching device is in a low state and needs to be turned on, it automatically turns on; when the switching device is in the on state and the terminal voltage of the switching device... The switching device is automatically turned off when it goes into a high state.
[0061] In addition, to improve the output stability of the voltage comparator circuit 3, in this embodiment, the output signal of the voltage comparator circuit 3 is also input to the threshold reference source 4, so that the reference voltage output by the threshold reference source 4 is... It can set the reference voltage based on the comparison result of voltage comparison circuit 3. It can change with the output state of voltage comparison circuit 3, thereby establishing a hysteresis curve to prevent jitter that may occur when the comparison circuit determines the comparison edge.
[0062] Figure 2 This embodiment demonstrates the state of the pull-up circuit 2 and the output zero-voltage detection signal ZVD-S of the detection circuit 1 during the switching process of the switching device being turned on and off.
[0063] When an overcurrent or short circuit occurs, the terminal voltage of the switching device... It will rise in a short time. Although the impedance of pull-up circuit 2 is high in the initial state of the switching device being turned on, its anti-interference capability is weak at this time. However, when voltage comparator circuit 3 detects the terminal voltage of the switching device... Exceeding the reference voltage At this time, based on the comparison result of voltage comparison circuit 3, switch S1 in pull-up circuit 2 is turned on. At this time, the low-resistance first pull-up resistor... When connected to the pull-up line, pull-up circuit 2 becomes a low-impedance state, and the detection voltage input to voltage comparator circuit 3 is simultaneously... The signal is reconfirmed with higher interference immunity by using a pull-up circuit 2 that becomes low impedance. False alarms caused by interference can also be quickly filtered out.
[0064] In practical applications, the controller can determine whether the circuit has an overcurrent or short circuit fault based on the suddenly interrupted zero voltage detection signal ZVD-S; it can also work with the gate driver 5 to form a self-sustaining conduction state by the gate enable signal Gate-EN and the zero voltage detection signal ZVD-S, and the switching device will be automatically turned off when either signal fails. Figure 3 This demonstrates a process example of automatic shutdown based on a zero-voltage detection signal.
[0065] The switching device (MOSFET) is controlled to turn on only when both the gate enable signal Gate-EN and the zero-voltage detection signal ZVD-S are logic "1". The direct control signal DC-S intervenes when the switching device needs to be turned on under hard switching conditions. It attempts to turn on the switching device by sending a short pulse when the detection circuit 1 has no low-state output (i.e., the output is logic "0"). The duration of this pulse should be shorter than the allowable short-circuit duration of the switching device.
[0066] The overall advantage of the zero-voltage detection and overcurrent / short-circuit detection circuit described in this invention is that its response delay is primarily determined by the response delay of the comparator in the voltage comparison circuit 3. Because it requires no or only a very small filter capacitor, the zero-voltage detection described in this invention maintains the same high-speed dynamic performance on both the rising and falling edges of the voltage at the switching device terminals. It provides a low-delay, fast response to timely turn-on under soft switching and to rapid voltage increases during overcurrent and short-circuit conditions. Furthermore, it does not incur significant static power consumption in pursuit of high anti-interference capability and low response delay.
[0067] In the second embodiment, refer to Figure 4 As shown, the difference from the first embodiment is that a more specific structure of the pull-up circuit 2, voltage comparison circuit 3, and threshold reference source 4 is shown.
[0068] In this embodiment, switch S1 is a P-channel field-effect transistor, and switch S1 is equipped with a corresponding driving circuit. The corresponding driving circuit controls its gate according to the output signal of voltage comparison circuit 3.
[0069] Furthermore, the voltage comparison circuit 3 includes a voltage comparator and a first voltage divider resistor R. c1 Second voltage divider resistor R c2 The first input terminal of voltage comparator circuit 3 is connected to threshold reference source 4; the second input terminal of voltage comparator circuit 3 is connected to the first voltage divider resistor R. c1 It is then connected between pull-up circuit 2 and isolation diode D, and passes through the second voltage divider resistor R. c2 The first pull-up power supply U1 is then connected to its negative terminal; the first voltage divider resistor R c1 With the second voltage divider resistor R c2 A voltage divider circuit is formed to obtain the detection voltage from voltage comparator circuit 3. The scaling is adjusted to match the input range allowed by the voltage comparator, and then compared with the reference voltage. Compare them.
[0070] Furthermore, the threshold reference source 4 includes a reference power supply U2 and a first reference resistor R. r1 Second reference resistor R r2The third reference resistor Rr3 is connected to the third reference resistor; the negative terminal of the reference power supply U2 is connected to the negative terminal of the pull-up power supply U1, and the positive terminal of the reference power supply U2 is connected to the first reference resistor R. r1 One end; the first reference resistor R r1 The other end serves as the output of the threshold reference source 4 and is connected to the first input of the voltage comparison circuit 3; furthermore, the output of the threshold reference source 4 is also connected to the second reference resistor R. r2 The output of the threshold reference source 4 is connected to the negative terminal of the reference power supply U2; the output of the threshold reference source 4 is also connected to the output of the voltage comparator circuit 3 through the third reference resistor Rr3, so that its output reference voltage... The output state of voltage comparator circuit 3 can be changed to generate two reference voltages with hysteresis curves. .
[0071] In practical design, the two power supplies can be designed independently. , To reduce the response delay of the zero-voltage detection circuit, a low-current Schottky diode (such as one based on silicon or silicon carbide) can be used as the isolation diode D. Due to the addition of a low-resistance pull-up resistor R1 in this invention, its resistance is reduced by the junction capacitance of the isolation diode. The interference of the charging and discharging current generated by the high voltage change rate during the switching process of the switching device (MOSFET) on the voltage detection circuit can be easily suppressed, so the isolation diode D can have a wide selection range.
[0072] Preferably, in the third embodiment, reference is made to Figure 5 As shown, the difference from the first embodiment is that a first delay circuit 6 is also provided between the output terminal of the voltage comparison circuit 3 and the control terminal of the switch S1.
[0073] The effect of adding the first delay circuit 6 is as follows: Figure 6 As shown, the turn-on operation of switch S1 is executed in real time, while its turn-off operation is executed with a delay. When the voltage comparator circuit 3 detects the terminal voltage of the switching device... After reaching the low state, the low impedance state of pull-up circuit 2 is extended and maintained for a period of time. During this period, the interference that the voltage comparison circuit 3 may encounter can be further suppressed by the pull-up circuit 2 in a low impedance state, thereby improving the overall anti-interference capability of the detection circuit.
[0074] This delay circuit can be composed of analog circuits and logic gates or implemented using digital circuits. Figure 7 A first delay circuit 6 based on analog circuitry is shown, with the signal input on the left and the signal output on the right. Through this circuit, the rising edge of the signal output by the voltage comparator circuit 3 is delayed by an RC circuit, while its falling edge is transmitted to the output in real time through an AND gate.
[0075] Specifically, in some applications, the function of the first delay circuit 6 can be provided by the driving circuit of switch S1. Figure 8 A drive circuit with integrated turn-off delay characteristics is demonstrated. Switch S1 is a P-channel MOSFET. When the signal output by the voltage comparator circuit 3 is logic "0", the inverter and the corresponding pull-down switch directly drive switch S1 to conduct. When the signal changes to logic "1", switch S1 is no longer actively driven to conduct. At this time, the gate capacitance and bypass resistor of switch S1 together provide the turn-off delay.
[0076] Preferably, in the fourth embodiment, reference is made to Figure 9 As shown, the difference from the first embodiment is that a second delay circuit 7 is also provided between the output terminal of the voltage comparison circuit 3 and the output terminal corresponding to the zero voltage detection signal ZVD-S.
[0077] The second delay circuit 7 processes the output of the zero-voltage detection signal ZVD-S, causing the terminal voltage of the corresponding switching device to... The zero-voltage detection signal ZVD-S when transitioning from a high state to a low state is output in real time, while the zero-voltage detection signal ZVD-S when transitioning from a low state to a high state is output with a delay, corresponding to the terminal voltage of the switching device. The low-state signal can reset its current delay state to obtain a higher anti-interference capability.
[0078] The effect of adding the second delay circuit 7 is as follows: Figure 10 As shown, when the output signal of voltage comparator circuit 3 is determined by the terminal voltage of the corresponding switching device... When the signal changes from a high state to a low state, it is output in real time. In this example, the zero-voltage detection signal ZVD-S changes from logic "0" to logic "1", which is the rising edge of the zero-voltage detection signal ZVD-S. And when this signal is changed by the terminal voltage of the corresponding switching device... When a state changes from a low state to a high state, the original state is maintained for a period of time. In this example, the logic signal changes from "1" to "0", which is the falling edge of the zero-voltage detection signal ZVD-S. During this period, the pull-up circuit 2, which switches to a low-impedance state, controls the voltage input to the voltage comparator circuit 3. Verification is performed to eliminate potential noise interference and improve the overall anti-interference capability of the detection circuit.
[0079] This delay circuit can be composed of analog circuits and logic gates or implemented using digital circuits. Figure 11A second delay circuit 7 based on analog circuitry is shown, with the signal input on the left and the signal output on the right. In this circuit, the falling edge of the signal output by the voltage comparator circuit 3 is delayed by an RC circuit, and the delay circuit is reset by a bypass diode when the signal becomes logic "1" again; while the rising edge of the signal is transmitted to the output in real time through an OR gate.
[0080] The delays generated by the first delay circuit 6 and the second delay circuit 7 are both in the range of tens to hundreds of nanoseconds, which do not have a significant impact on the real-time performance of the entire circuit.
[0081] Preferably, in the fifth embodiment, referring to Figure 12 As shown, to further enhance the voltage at the switching device terminals of the detection circuit 1 To improve the response speed at the rising edge, a capacitor C1 can be connected in parallel with the first pull-up resistor R1. The capacitance value of capacitor C1 can be selected from tens to hundreds of picofarads, for example, 20pF to 200pF. The effect is that when switch S1 is turned on, this capacitor can further reduce the transient impedance of the low-resistance pull-up circuit 2, thereby accelerating the response of the voltage comparator circuit 3 to the detected voltage. The rising edge confirmation process. This reduces response delay and also improves the anti-interference capability of the entire detection circuit.
[0082] It is understood that in other embodiments, the optimization methods described in the third to fifth embodiments above can also be used in combination.
[0083] In summary, compared with existing technologies, the low-response-delay zero-voltage detection and overcurrent / short-circuit detection circuit provided by this invention utilizes the output state of the voltage comparison circuit built into the detection circuit to connect resistors of different resistance values into the pull-up circuit. This allows the pull-up circuit to maintain a low impedance during the detection phase, thereby improving anti-interference capability while achieving low response delay performance, and switches to a high impedance state after detection to reduce static losses. This offers the following advantages:
[0084] 1) The filter capacitor located at the input of the voltage comparator circuit can be directly eliminated or only a very small capacitance specification can be used, thereby significantly reducing the response delay of the voltage detection circuit and providing voltage state detection capability with the same low delay performance at both the rising and falling edges of the voltage at the switching device.
[0085] 2) Since the interference generated by the junction capacitance of the isolation diode during charging and discharging can be suppressed by adjusting the resistance value in the pull-up circuit, it can be compatible with a wide range of isolation diodes, thereby reducing the difficulty of device selection and improving device compatibility.
[0086] 3) By automatically switching the pull-up circuit to a low-impedance state when the terminal voltage of the switching device is in the measured high state, the anti-interference capability of the voltage detection circuit is improved, and the reliability of the detection results is enhanced. Conversely, by automatically switching the pull-up resistor to a high-impedance state when the terminal voltage of the switching device is in the low state, the static loss of the voltage detection circuit is reduced.
[0087] 4) It eliminates the need for large-capacity filter capacitors found in traditional circuits (which are approximately several nF in conventional circuits). The entire detection circuit consists of transistors (such as P-channel MOSFETs as switches S1, comparators, etc.) and resistors, making it more compatible with integrated design.
[0088] Finally, it should be noted that the above description is only an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.
Claims
1. A low-response-delay zero-voltage detection and overcurrent / short-circuit detection circuit for rapidly detecting the terminal voltage of switching devices. The state; Its features are, The low-response-delay zero-voltage detection and overcurrent short-circuit detection circuit (1) includes a pull-up power supply U1, a pull-up circuit (2), a voltage comparison circuit (3), a threshold reference source (4), and an isolation diode D; The pull-up circuit (2) includes a first pull-up resistor R1 and a second pull-up resistor R connected in parallel. H Furthermore, the branch containing the first pull-up resistor R1 is connected in series with a switch S1, and the on / off state of the switch S1 is controlled by the voltage comparison circuit (3). One end of the main circuit of the pull-up circuit (2) is connected to the positive terminal of the pull-up power supply U1, and the other end is connected to the anode of the isolation diode D; The cathode of the isolation diode D is connected to one end of the switching device, and the other end of the switching device is connected to the negative terminal of the pull-up power supply U1. The first input terminal of the voltage comparison circuit (3) is connected to the threshold reference source (4) to obtain the reference voltage. The second input terminal is connected between the pull-up circuit (2) and the isolation diode D to obtain the detection voltage corresponding to the terminal voltage of the switching device. ; The output terminal of the voltage comparison circuit (3) is connected to the control terminal of the switch S1; The voltage comparison circuit (3) according to and The comparison result is used to output a corresponding signal to the control terminal of the switch S1, and the signal is used as the output signal of the low response delay zero voltage detection and overcurrent short circuit detection circuit (1), that is, the zero voltage detection signal ZVD-S is output to the outside.
2. The low-response-delay zero-voltage detection and overcurrent / short-circuit detection circuit according to claim 1, characterized in that, When the voltage comparison circuit (3) detects the terminal voltage of the switching device When it is in a high state, that is When the switch S1 is turned on, the output signal controls the switch to conduct and outputs the terminal voltage corresponding to the switching device. The zero-voltage detection signal ZVD-S is in a high state; when the voltage comparison circuit (3) detects the terminal voltage of the switching device... When it is in a low state, that is When the switch S1 is open, the output signal controls the switch to open and outputs the terminal voltage corresponding to the switching device. The zero-voltage detection signal ZVD-S is for the low-state condition.
3. The low-response-delay zero-voltage detection and overcurrent / short-circuit detection circuit according to claim 1, characterized in that, The second pull-up resistor R H The resistance value is greater than the resistance value of the first pull-up resistor R1.
4. The low-response-delay zero-voltage detection and overcurrent / short-circuit detection circuit according to claim 1, characterized in that, The switch S1 is a field-effect transistor and is equipped with a corresponding driving circuit. The corresponding driving circuit controls its gate according to the output signal of the voltage comparison circuit (3).
5. The low-response-delay zero-voltage detection and overcurrent / short-circuit detection circuit according to claim 1, characterized in that, In the pull-up circuit (2), the first pull-up resistor R1 and the switch S1 are integrated into a single device, that is, the on-resistance of the switch S1 is R1.
6. The low-response-delay zero-voltage detection and overcurrent / short-circuit detection circuit according to claim 1, characterized in that, A first delay circuit (6) is also provided between the output terminal of the voltage comparison circuit (3) and the control terminal of the switch S1, so that the conduction operation of the switch S1 is executed in real time, while its turn-off operation is executed with a delay.
7. The low-response-delay zero-voltage detection and overcurrent / short-circuit detection circuit according to claim 1, characterized in that, A second delay circuit (7) is also provided between the output terminal of the voltage comparison circuit (3) and the output terminal corresponding to the zero voltage detection signal ZVD-S, so that the terminal voltage of the corresponding switching device is reduced. The zero-voltage detection signal ZVD-S when changing from a high state to a low state is output in real time, while the zero-voltage detection signal ZVD-S when changing from a low state to a high state is output with a delay.
8. The low-response-delay zero-voltage detection and overcurrent / short-circuit detection circuit according to claim 1, characterized in that, A capacitor C1 is connected in parallel with the first pull-up resistor R1 to further reduce the transient impedance of the pull-up circuit (2) when the switch S1 is turned on.
9. The low-response-delay zero-voltage detection and overcurrent / short-circuit detection circuit according to claim 1, characterized in that, The switching device is equipped with a gate driver (5), which is used to control the gate voltage of the switching device, thereby controlling the on / off state of the switching device; The zero-voltage detection signal ZVD-S output by the low-response-delay zero-voltage detection and overcurrent / short-circuit detection circuit (1) is also input to the gate driver (5). When the terminal voltage of the switching device... When the state is low, the switching device is automatically turned on when it needs to be turned on; When the switching device is in the ON state, and the terminal voltage of the switching device... The switching device is automatically turned off when it goes into a high state.
10. The low-response-delay zero-voltage detection and overcurrent / short-circuit detection circuit according to claim 1, characterized in that, The output signal of the voltage comparison circuit (3) is also input to the threshold reference source (4), so that the reference voltage output by the threshold reference source (4) is... It can be set according to the comparison result of the voltage comparison circuit (3).