Radiation-hardened temperature-compensated delay undervoltage lockout and overvoltage shutdown

Abstract

A circuit includes: a voltage detection path having a first transistor; and a second transistor connected to the first voltage detection path via a first terminal of the second transistor. The first voltage detection path includes: a first current source; and a first voltage divider unit connected to the first current source. The first transistor is connected to the first voltage divider unit via a first terminal of the first transistor. A first voltage value at a second terminal of the first transistor is configured to switch between a first high voltage value and a first low voltage value, at least partially based on a first detected voltage value provided by the first voltage divider unit at the first terminal of the first transistor. A second voltage at a second terminal of the second transistor is configured to switch between a second high voltage value and a second low voltage value, at least partially based on the first voltage value at the second terminal of the first transistor.

Description

Technical Field

[0001] This disclosure generally relates to voltage control of power drivers. Background Technology

[0002] A DC / DC converter is a power supply that converts an input DC voltage into different output DC voltages. Such a converter typically includes a transformer electrically connected between the voltage source and the load via a switching circuit. A converter, known as a forward converter, includes at least one main switch connected between the voltage source and the primary winding of the transformer to provide forward power transfer to the secondary winding of the transformer when the switch is turned on and off.

[0003] Voltage monitors are used in a wide variety of voltage sensing applications, including DC / DC converters or any circuit requiring undervoltage and / or overvoltage detection. These devices provide circuit designers with an economical solution for positive and negative voltage sensing. These devices typically include a comparator with an internal voltage reference and an output indicating overvoltage or undervoltage detection. The output is driven low when the voltage at the sensing pin drops below a negative threshold, and driven high when the voltage at the sensing pin increases above a positive threshold. The comparator typically includes built-in hysteresis for noise suppression, ensuring stable output operation without false triggering. In some cases, voltage monitor devices include a comparator channel that can be configured to be inverting or non-inverting, enabling undervoltage detection, overvoltage detection, or window voltage detection.

[0004] Applications with high levels of ionizing radiation present unique design challenges for voltage monitoring. A single charged particle can knock down thousands of electrons, causing electronic noise and signal spikes. In the case of voltage monitoring circuits, this can lead to inaccurate or incomprehensible results. This can be a particularly serious problem in the design of components used in satellites, spacecraft, aircraft, power plants, and the like. Summary of the Invention

[0005] A circuit includes an undervoltage detection path and an overvoltage detection path. The undervoltage detection path includes: a first current source; a first voltage divider unit connected to the first current source; and a first transistor connected to the first voltage divider unit via a first terminal of the first transistor, wherein a first voltage value at a second terminal of the first transistor is configured to switch between a first high voltage value and a first low voltage value based at least partially on a first detection voltage value provided by the first voltage divider unit at the first terminal of the first transistor. The overvoltage detection path includes: a second current source; a second voltage divider unit connected to the second current source; and a second transistor connected to the second voltage divider unit via a first terminal of the second transistor, wherein a second voltage value at a second terminal of the second transistor is configured to switch between a second high voltage value and a second low voltage value based at least partially on a second detection voltage value provided by the second voltage divider unit at the first terminal of the second transistor, and the second terminal of the second transistor is connected to the first terminal of the first transistor.

[0006] A circuit includes a comparator, a capacitor, and a diode. The comparator includes: a first input terminal configured to be connected to a reference voltage; and a second input terminal connected to a first terminal of the capacitor. The first terminal of the capacitor is configured to be connected to a voltage source via a resistive path, and the second terminal of the capacitor is connected to ground. The negative terminal of the diode is configured to be connected to a voltage signal switching between high and low values, and the positive terminal of the diode is connected to the first terminal of the capacitor.

[0007] Advantageously, one or more embodiments discussed herein monitor voltage using discrete or analog devices and minimal integrated circuits. This provides complete control and ownership of the design, as well as a selection of components that allow for a wide range of configurations, including configurations providing a variety of output power ranges and levels of radiation hardness. Attached Figure Description

[0008] In the accompanying drawings, the same reference numerals denote similar elements or actions. The dimensions and relative positions of the elements in the drawings need not be drawn to scale. For example, the shapes of various elements and angles need not be drawn to scale, and some of these elements may be arbitrarily enlarged and positioned to improve the readability of the drawing. Furthermore, the specific shapes of the elements shown in the figures are not necessarily intended to convey any information about the actual shape of the particular element and may be chosen solely for ease of identification in the accompanying drawings.

[0009] Figure 1 This is an example circuit diagram based on the implementation scheme shown.

[0010] Figure 2 Showing according to Figure 1 Example signal waveforms for some of the operations shown in the example circuit. Detailed Implementation

[0011] In the following description, certain specific details are set forth to provide a thorough understanding of the various disclosed embodiments. However, those skilled in the art will recognize that the embodiments can be practiced without one or more of these specific details, or using other methods, components, materials, etc. In other instances, well-known structures associated with the circuits have not been shown or described in detail to avoid unnecessarily obscuring the description of the embodiments.

[0012] Unless the context otherwise requires, throughout the specification and the appended claims, the word “comprising” is synonymous with “including” and is inclusive or open-ended (i.e., does not exclude additional, unlisted elements or methodological actions).

[0013] Throughout this specification, references to "an embodiment" or "an embodiment" mean that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment. Therefore, the phrases "in an embodiment" or "in an embodiment" appearing in various places throughout this specification do not necessarily refer to the same embodiment. Furthermore, particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0014] As used in this specification and the appended claims, the singular forms “a”, “an”, and “the” include plural indicators unless the context clearly specifies otherwise. It should also be noted that the term “or” is generally used in its sense as including “and / or” unless the context clearly specifies otherwise.

[0015] The titles and abstracts of this disclosure provided herein are for convenience only and do not constitute an explanation of the scope or meaning of the embodiments.

[0016] One or more embodiments of this disclosure provide a voltage monitoring circuit formed using discrete analog components. Figure 1 A schematic diagram of a voltage monitoring circuit 100 according to an exemplary embodiment of the present disclosure is shown. In the illustrated embodiment, the voltage monitoring circuit 100 includes a voltage detection stage 102 and an output stage 104.

[0017] The voltage detection stage 102 includes an undervoltage detection path 110, an overvoltage detection path 140, and a detection signal generation unit 170.

[0018] In one or more embodiments, the undervoltage detection path 110 includes a transistor 112 (e.g., implemented by an NPN bipolar junction transistor (BJT)) connected to the voltage Vin to be monitored via a voltage divider unit 114 and a current source unit 116. The voltage divider unit 114 is configured to provide a detection voltage corresponding to the voltage Vin at the base terminal 112b of the NPN BJT 112. In some embodiments, the voltage divider unit 114 is configured to provide a voltage at the base terminal 112b of the NPN BJT 112 equal to a fraction or ratio of the voltage Vin to be monitored. In some embodiments, the voltage divider unit 114 includes a resistor 118 connected between the base terminal 112b of the NPN BJT 112 and the voltage Vin to be monitored. The voltage divider unit 114 also includes a resistor 120 connected between the base terminal 112b of the NPN BJT 112 and a negative voltage source (e.g., ground). In some embodiments, the current source unit 116 is connected between the voltage divider unit 114 and the voltage to be detected Vin, although other embodiments are possible and are included in this disclosure. For example, the current source unit 116 may also be connected between the voltage divider unit 114 and a ground reference.

[0019] In some embodiments, the voltage divider unit 114 includes one or more Zener diodes 122 (one Zener diode 122 is shown for illustration) connected in series between the base 112b and the resistor 118, wherein the cathode terminal of the Zener diode 122 is connected to the resistor 118, and the anode is connected to the resistor 120. The Zener diode 122 is configured to establish a relatively fixed voltage difference or voltage step, known as the Zener voltage, in the voltage divider unit 114.

[0020] The emitter terminal 112e of the NPN BJT 112 is connected to ground. When the NPN BJT 112 is off, the collector terminal 112c of the NPN BJT 112 is connected to a high voltage. When the NPN BJT 112 is on, the collector terminal 112c of the NPN BJT 112 is connected to ground and is at a low voltage value. The on and off states of the NPN BJT 112 are controlled by a sensed voltage value at the base terminal 112b. That is, the voltage at the collector terminal 112c switches between high and low values ​​based on the voltage value at the base terminal 112b.

[0021] In some implementations, the collector 112c is coupled to the detection signal generation unit 170, which is described in further detail herein.

[0022] In some implementations, the parameters of resistors 118, 120, and Zener diode 122 are configured to compensate for the temperature coefficient of the base-emitter voltage (Vbe) of the NPN BJT 112, so that the detection of the undervoltage state of the voltage Vin to be detected is unaffected by temperature changes. The temperature coefficient of Zener diode 122 is positive, and the temperature coefficient of Vbe of the NPN BJT 112 is negative. However, the temperature coefficients of Zener diode 122 and Vbe of the NPN BJT 112 can have different magnitudes. Typically, the temperature coefficient of Zener diode 122 has a larger magnitude than the temperature coefficient of Vbe of the NPN BJT 112. In some implementations, the parameters of resistors 118, 120, and Zener diode 122 are configured based on the following algorithm:

[0023]

[0024] Among them, Tempco Vbe It is the temperature coefficient of Vbe for NPN BJT 112; Tempco Zener R is the temperature coefficient of the Zener diode 122; 118 It is the resistance value of resistor 118; and R 120 This is the resistance value of a 120Ω resistor.

[0025] In some implementations, the ratio between resistors 118 and 120 has some design limitations due to the design requirements of voltage divider unit 114. The temperature coefficient of Zener diode 122 can be adjusted by selecting one or more Zener diodes with varying Zener voltages. Generally, the higher the Zener voltage, the higher the temperature coefficient, as the Zener voltage is above 5V. Various combinations of two or more Zener diodes will provide varying Zener voltages and temperature coefficients. For example, a total Zener voltage of approximately 12V can be achieved by two Zener diodes, each at 6V, or by a 3V Zener diode and a 9V Zener diode. Two exemplary combinations of Zener diodes will have different temperature coefficients. Therefore, although in Figure 1 Only a single Zener diode 122 is shown, but in practice one or more Zener diodes can be provided to achieve the desired Zener voltage and temperature coefficient.

[0026] In one or more embodiments, the overvoltage detection path 140 includes a switch 142 (e.g., implemented by an NPN bipolar junction transistor (BJT)) connected to the voltage to be monitored, Vin, via a voltage supply unit (e.g., a voltage divider unit 144 and a current source unit 146). The voltage divider unit 144 is configured to provide a detection voltage corresponding to the voltage to be monitored, Vin, at the base terminal 142b of the NPN BJT 142. In some embodiments, the voltage divider unit 144 provides a voltage at the base terminal 142b of the NPN BJT 142 equal to a fraction or ratio of the voltage to be monitored, Vin. In some embodiments, the voltage divider unit 144 includes a resistor 148 connected between the base terminal 142b of the NPN BJT 142 and the voltage to be monitored, Vin. The voltage divider unit 144 also includes a resistor 150 connected between the base terminal 142b of the NPN BJT 142 and ground. In some embodiments, the current source unit 146 is connected between the voltage divider unit 144 and the voltage to be detected Vin, although other embodiments are possible and are included in this disclosure. For example, the current source unit 146 may also be connected between the voltage divider unit 144 and ground.

[0027] In some implementations, each of the current sources 116, 146 can be implemented using discrete components such as resistors and bipolar junction transistors.

[0028] Regarding the same voltage value of the voltage to be detected, Vin, for example, when both overvoltage detection path 140 and undervoltage detection path 110 are connected to the same voltage to be detected, voltage divider unit 144 is configured to provide a smaller detection voltage to base terminal 142b of NPN BJT 142 than the detection voltage provided by voltage divider unit 114 to base terminal 112b of NPN BJT 112, for example, a smaller ratio of Vin. For example, voltage divider unit 144 is configured to provide a portion of the voltage to be detected at base terminal 142b that is smaller than the portion of the voltage to be detected Vin provided by voltage divider unit 114 at base terminal 112b. In some embodiments, resistor 150 has a smaller resistance value than resistor 120, and resistor 148 has a larger resistance value than resistor 118.

[0029] In some implementations, the voltage divider unit 144 includes one or more Zener diodes (two shown) 152 connected in series between the base terminal 142b and the resistor 148, wherein the negative terminal of the top (as shown) Zener diode 152 is connected to the resistor 148. The selection of parameters for the one or more Zener diodes 152 can take into account the Zener voltage and temperature coefficient of each Zener diode 152.

[0030] The emitter 142e of the NPN BJT 142 is connected to ground. The collector terminal 142c of the NPN BJT 142 is connected to the base terminal 112b of the NPN BJT 112. Thus, the NPN BJT 142 is effectively a switch for the voltage supplied to the base terminal 112b of the NPN BJT 112 by the voltage divider unit 114. When the NPN BJT 142 is on, the base terminal 112b of the NPN BJT 112 is pulled down to ground, and the voltage divider unit 114 is bypassed and does not supply a voltage signal to the base terminal 112b of the NPN BJT 112. When the NPN BJT 142 is off, the voltage divider unit 114 provides a sense voltage to the base terminal 112b of the NPN BJT 112. Thus, the detection voltage on the base terminal 142b of the NPN BJT 142 controls the voltage level at the collector terminal 112c of the NPN BJT 112.

[0031] In some implementations, similar to undervoltage detection path 110, the parameters of resistors 148, 150, and Zener diode 152 are configured to compensate for the temperature coefficient of Vbe of NPN BJT 142.

[0032] The detection signal generation unit 170 includes an NPN BJT 172. The base terminal 172b of the NPN BJT 172 is connected to the collector terminal 112c of the NPN BJT 112. The base terminal 172b of the NPN BJT 172 is also connected to a voltage source Vcc via a resistor 174 or a voltage divider unit including the resistor 174. The emitter terminal 172e of the NPN BJT 172 is connected to ground. Thus, the NPN BJT 112 effectively functions as a switch to control the ground voltage or high voltage value to be applied to the base terminal 172b of the NPN BJT 172. Specifically, when the NPN BJT 112 is turned on, a ground voltage value is applied to the base terminal 172b of the NPN BJT 172. When the NPN BJT 112 is turned off, a high voltage value is applied to the base terminal 172b of the NPN BJT 172.

[0033] In some implementations, the detection signal generation unit 170 includes a capacitor 176 connected between the base terminal 172b and ground. As discussed above, the capacitor 176 enables a delayed change in the voltage value that can be applied to the base terminal 172b of the NPN BJT 172, controlled by the NPN BJT 112 acting as a switch. For example, when the NPN BJT 112 is turned on, the capacitor 176 discharges to ground through the NPN BJT 112, and after the delay, the voltage at the base terminal 172b switches from a high value to a low value or ground. When the NPN BJT 112 is turned off, the capacitor 176 is charged by the voltage source Vcc through the resistor 124. After the delay, the voltage at the base terminal 172b switches from a low value to a high value.

[0034] When the voltage at the base terminal 172b of the NPN BJT 112 is low, the NPN BJT 172 is off, and the collector terminal 172c of the NPN BJT 112 is switched to a high voltage level by being connected to the voltage source Vcc via resistor 174. When the voltage at the base terminal 172b of the NPN BJT 112 is high, the NPN BJT 172 is on, and the collector terminal 172c of the NPN BJT 112 is switched to a low voltage level by being connected to ground.

[0035] In some embodiments, the undervoltage detection path 110 and the overvoltage detection path 140 each include a positive feedback path. The positive feedback paths enhance the detection results of the undervoltage detection path 110 and the overvoltage detection path 140, respectively. In some embodiments, the positive feedback path of the undervoltage detection path 110 includes a resistor 126 connected between the collector terminal 172c of the NPN BJT 172 and the base terminal 112b of the NPN BJT 112. In some embodiments, a Zener diode 122 is part of the feedback path and is connected to the resistor 126 and the base terminal 112b of the NPN BJT 112, which does not limit the scope of this disclosure. For example, the feedback path resistor 126 may be directly connected to the base terminal 112b of the NPN BJT 112.

[0036] In some embodiments, the positive feedback path of the overvoltage detection path 140 includes a resistor 156 connected between the collector terminal 112c of the NPN BJT 112 and the base terminal 142b of the NPN BJT 142. In some embodiments, the feedback path resistor 126 is directly connected to the base terminal 142b of the NPN BJT 142, which does not limit the scope of this disclosure. For example, one or more Zener diodes 152 may be part of the feedback path and may be connected between the resistor 156 and the base terminal 142b of the NPN BJT 142.

[0037] Positive feedback paths enhance the detection results of undervoltage detection path 110 and overvoltage detection path 140, respectively. Regarding undervoltage detection path 110, when the detected voltage at the base terminal 112b of NPN BJT 112 is low, NPN BJT 112 is turned off, and NPN BJT 172 is turned on. The feedback path resistor 126 is effectively connected in parallel with the resistor 120 of the voltage divider unit 114, which further reduces the voltage at the base terminal 112b of NPN BJT 112. When the detected voltage at the base terminal 112b of NPN BJT 112 is high, NPN BJT 112 is turned on, and NPN BJT 172 is turned off. The high voltage level at the collector terminal 172c of the NPN BJT172 is fed back to the base terminal 112b of the NPN BJT 112 through the feedback path resistor 126, which further increases the voltage at the base terminal 112b of the NPN BJT 112.

[0038] Regarding the overvoltage detection path 140, when the detected voltage at the base terminal 142b of NPN BJT 142 is low, NPN BJT 142 is off, and NPN BJT 112 is on. The feedback path resistor 156 is effectively connected in parallel with the resistor 150 of the voltage divider unit 144, which further reduces the voltage at the base terminal 142b of NPN BJT 142. When the detected voltage at the base terminal 142b of NPN BJT 142 is high, NPN BJT 142 is on, and NPN BJT 112 is off. The high voltage level at the collector terminal 112c of NPN BJT 112 is fed back to the base terminal 142b of NPN BJT 112 through the feedback path resistor 156, which further increases the voltage at the base terminal 142b of NPN BJT 142.

[0039] In some implementations, the collector terminal 172c of the NPN BJT 172 is configured as an output terminal of the detection signal generation unit 170 and is connected to the output stage 104.

[0040] Output stage 104 includes a comparator 180 having a first differential input terminal (e.g., a positive input terminal or a non-inverting input terminal) and a second differential input terminal (e.g., a negative input terminal or an inverting input terminal). The negative input terminal of comparator 180 is connected to a reference voltage. In some embodiments, the reference voltage is provided by a voltage divider unit 182 connected to a voltage source Vcc. The voltage divider unit 182 includes a resistor 184 connected between the negative input terminal of comparator 180 and the voltage source Vcc, and a resistor 186 connected between the negative input terminal of comparator 180 and ground. A capacitor 190 is connected to the positive input of comparator 180 and ground. A first terminal of the capacitor is connected to the positive input of comparator 180 and, through resistor 192, to the voltage source Vcc. A second terminal of the capacitor 190 is connected to ground.

[0041] The first terminal of capacitor 190 is connected to the output terminal of detection signal generation unit 170, such as the collector terminal 172c of NPN BJT 172, via diode 194. Specifically, the cathode of diode 194 is connected to the collector terminal 172c of NPN BJT 172, and the anode of diode 194 is connected to the first terminal of capacitor 190.

[0042] In operation, when the output terminal (i.e., collector terminal 172c) of the detection signal generation unit 170 is high, capacitor 190 is charged by voltage source Vcc through resistor 192. After a delay configured based on the RC time constant of resistor 192 and capacitor 190, capacitor 190 is charged to a voltage higher than the reference voltage at the negative input terminal of comparator 180, and comparator 180 switches its output to a first output value. When the output terminal of the detection signal generation unit 170 is low, capacitor 190 discharges rapidly through diode 194, for example, because the resistance of diode 194 is very low. With a very small delay, the voltage at the first terminal of the capacitor, i.e., the voltage at the positive input terminal of comparator 180, becomes lower than the reference voltage at the negative input terminal of comparator 180, and comparator 180 switches its output to a second output value.

[0043] Figure 2 Chart 200 shows the signal waveforms of the voltage to be detected Vin, the output of the detection signal generation unit 170, the voltage of the capacitor 190, and the output of the output stage 104.

[0044] Refer to together Figure 1 and Figure 2In operation, when the voltage value of the voltage to be detected, Vin 210, is lower than the first threshold level TH1, for example, an undervoltage level, the detection voltage at the base terminal 112b of the NPN BJT 112 is lower than Vbe of the NPN BJT 112, and the NPN BJT 112 is turned off. Furthermore, the voltage at the collector terminal 112c of the NPN BJT 112 is switched to a high value, for example, by being connected to the voltage source Vcc via a resistive voltage divider formed by resistors 124, 156, and 150.

[0045] With a high voltage at the collector terminal 112c of the base terminal 172b of the NPN BJT 172, the NPN BJT 172 is turned on, and the voltage 220 at the collector terminal 172c of the NPN BJT 172 is pulled down to a low value, such as ground. This low voltage at the collector terminal 172c is fed back through resistor 126 to further pull down the voltage at the base terminal 112b of the NPN BJT 112, which reinforces the state change. For example, resistor 126 is effectively connected in parallel with Zener diode 122 and resistor 120, which further reduces the voltage at the negative terminal of Zener diode 122. That is, resistor 126 forms a positive feedback loop.

[0046] As the voltage 220 at the collector terminal 172c of the NPN BJT 172 reaches a low value, i.e., a low voltage value at the output of the detection signal generation unit 170, the capacitor 190 is discharged and the voltage 230 of the capacitor 190 is low. The output 240 of the comparator 180 is low as the first output, indicating that an undervoltage condition or overvoltage condition has been detected for the voltage Vin to be detected.

[0047] When the voltage value of the voltage to be detected Vin increases above the first threshold level TH1, the voltage at the base terminal 112b of the NPN BJT 112 increases above Vbe of the NPN BJT 112, and the NPN BJT 112 turns on. The voltage at the collector terminal 112c of the NPN BJT 112 is pulled down to a low value, such as ground.

[0048] With a low voltage at collector terminal 112c, NPN BJT 172 is turned off, and the voltage 220 at collector terminal 172c of NPN BJT 172 is switched to a high value, for example, by being connected to the voltage source Vcc via a resistive voltage divider formed by resistors 174, 126, and 120. The high voltage at collector terminal 172c is fed back through resistor 126 to further pull up or reinforce the high voltage at base terminal 112b of NPN BJT 112, which reinforces the state change. That is, resistor 126 forms a positive feedback loop.

[0049] As the voltage 220 at the collector terminal 172c of the NPN BJT 172 reaches a high value, capacitor 190 begins to charge, and the voltage 230 of capacitor 190 increases with the slope configured by the RC time constant during charging of capacitor 190 through resistor 192. When voltage 230 exceeds the reference voltage Vref at the negative input of comparator 180, output 240 of comparator 180 switches to a high value as a second output, indicating that the voltage value of the detected voltage Vin is in the normal operating range. The delay in switching to the second output value of output 240 ensures smooth turn-on of the relevant system (e.g., a power converter) when the detected voltage Vin changes from an abnormal state to a normal state. The delay can be adjusted by adjusting the parameters of one or more of capacitor 190 or resistor 192 to adjust the RC time constant during charging of capacitor 190.

[0050] Due to different voltage divider settings, the detection voltage at base terminal 142b of NPN BJT 142 is less than the detection voltage at base terminal 112b of NPN BJT 112. Based on the parameters of NPN BJT 112 and NPN BJT 142, there exists a normal range for the sensing voltage Vin, at which the detection voltage at base terminal 112b is greater than Vbe of NPN BJT 112, and the detection voltage at base terminal 142b of NPN BJT 142 is less than Vbe of NPN BJT 142. That is, NPN BJT 112 is on and NPN BJT 142 is off. In some embodiments, NPN BJT 112 and NPN BJT 142 are identical in parameters.

[0051] When the voltage 210 at the detected voltage Vin further increases to the second threshold level TH2, the voltage at the base terminal 142b of the NPN BJT 142 increases above Vbe of the NPN BJT 142, the NPN BJT 142 turns on, and the voltage at the collector terminal 142c of the NPN BJT 142 is pulled down to a low value, such as ground.

[0052] With a low voltage value at the collector terminal 142c of the base terminal 112b of the NPN BJT 112, the NPN BJT 112 is turned off, and the voltage at the collector terminal 112c of the NPN BJT 112 switches to a high value.

[0053] The high voltage at collector terminal 112c is fed back to base terminal 142b of NPN BJT 142 through resistor 156 to further pull up or enhance the high voltage at base terminal 142b of NPN BJT 142. That is, resistor 156 forms positive feedback.

[0054] When a high voltage is applied to the collector terminal 112c of the base terminal 172b of the NPN BJT 172, the NPN BJT 172 is turned on, and the voltage 220 at the collector terminal 172c of the NPN BJT 172 is pulled down to a low value, such as ground. This low voltage at the collector terminal 172c is fed back through resistor 126 to further pull down the voltage at the base terminal 112b of the NPN BJT 112, thus reinforcing the state change.

[0055] As the voltage 220 at the collector terminal 172c of the NPN BJT 172 becomes low, the capacitor 190 discharges rapidly through the diode 194, and the voltage 230 of the capacitor 190 switches to a low value. The output 240 of the comparator 180 switches to a low value, i.e., the first output, indicating that an undervoltage or overvoltage condition has been detected for the voltage Vin to be detected.

[0056] When the voltage 210 at the detected voltage Vin decreases to a value below the second threshold TH2 and above the first threshold TH1, i.e., when the detected voltage Vin is in normal operating condition, NPN BJT 142 is turned off, NPN BJT 112 is turned on, and NPNBJT 172 is turned off. Capacitor 190 is charged. When capacitor 190 is charged to a voltage greater than the reference voltage Vref, with a delay after the voltage 210 at the detected voltage Vin has decreased to the normal range, the output of comparator 180 switches to the second output, indicating that the system can be turned on.

[0057] The foregoing detailed description has illustrated various embodiments of apparatus and / or processes using block diagrams, schematic diagrams, and examples. Where such block diagrams, schematic diagrams, and examples contain one or more functions and / or operations, those skilled in the art will understand that each function and / or operation within such block diagrams, flowcharts, or examples can be implemented individually and / or collectively by a wide range of hardware, software, firmware, or virtually any combination thereof. In one implementation, this subject matter can be implemented using an application-specific integrated circuit (ASIC). However, those skilled in the art will recognize that the embodiments disclosed herein can be implemented, wholly or partially, equivalently in standard integrated circuits, as one or more computer programs running on one or more computers, as firmware, or as virtually any combination thereof, and that designing the circuitry and / or writing the code for the software and / or firmware will be entirely within the skill of those of ordinary skill in the art according to this disclosure.

[0058] Those skilled in the art will recognize that many of the methods or algorithms described herein may employ additional actions, omit some actions, and / or perform actions in a different order than specified.

[0059] Furthermore, those skilled in the art will understand that the mechanisms taught herein can be distributed as program products in various forms, and the illustrative embodiments are equally applicable regardless of the specific type of signal-bearing medium used to actually perform the distribution. Examples of signal-bearing media include, but are not limited to, recordable media such as floppy disks, hard disk drives, CD-ROMs, digital magnetic tapes, and computer memory.

[0060] The various embodiments described above can be combined to provide further embodiments. Based on the detailed description above, these and other changes can be made to the implementation. Generally, the terminology used in the appended claims should not be construed as limiting the claims to the specific embodiments disclosed in the specification and claims, but should be construed as including all possible embodiments and the full scope of equivalents authorized by these claims. Therefore, the claims are not limited by this disclosure.

[0061] U.S. Patent Application No. 17 / 461,814, filed August 30, 2021 (which claims priority hereof), is incorporated herein by reference in its entirety.

Claims

1. A circuit comprising: The first voltage detection path has a first transistor; as well as The second transistor is connected to the first voltage detection path through the first terminal of the second transistor; The first voltage detection path includes: First current source; and A first voltage divider unit is connected to the first current source. The first transistor is connected to the first voltage divider unit via a first terminal of the first transistor. A first voltage value at a second terminal of the first transistor is configured to switch between a first high voltage value and a first low voltage value, at least in part based on a first detected voltage value provided by the first voltage divider unit at the first terminal of the first transistor. The second voltage at the second terminal of the second transistor is configured to switch between a second high voltage value and a second low voltage value, at least in part based on the first voltage value at the second terminal of the first transistor.

2. The circuit of claim 1, wherein, The first voltage divider unit includes a Zener diode, the positive terminal of which is connected to the first terminal of the first transistor.

3. The circuit of claim 2, wherein, The first voltage divider unit includes a first resistor and a second resistor. The first resistor is connected between the first terminal of the first transistor and ground, and the Zener diode is connected in series between the second resistor and the first terminal of the first transistor.

4. The circuit of claim 3, wherein, The first transistor is an NPN bipolar junction transistor, the NPN bipolar junction transistor having a first Vbe with a first temperature coefficient, and the Zener diode having a second temperature coefficient, wherein: Among them, Tempco Vbe The first temperature coefficient, Tempco, represents the first Vbe. Zener R1 represents the resistance of the first resistor, and R2 represents the resistance of the second resistor.

5. The circuit of claim 1, wherein, The first voltage detection path is connected to the voltage to be detected.

6. The circuit of claim 1, comprising a feedback path between the second terminal of the second transistor and the first terminal of the first transistor.

7. The circuit of claim 6, wherein, The feedback path includes a third resistor.

8. The circuit according to claim 1, comprising an output stage, said output stage including a comparator, a capacitor, and a diode, wherein: The comparator includes: a first input terminal configured to be connected to a reference voltage; and a second input terminal connected to the first terminal of the capacitor; The negative terminal of the diode is connected to the second terminal of the second transistor, and the positive terminal of the diode is connected to the first terminal of the capacitor; and The first terminal of the capacitor is configured to be connected to a voltage source via a resistor path.

9. The circuit according to claim 1, further comprising a second voltage detection path, the second voltage detection path comprising: Second current source; The second voltage divider unit is connected to the second current source; as well as A third transistor is connected to the second voltage divider unit via a first terminal of the third transistor, and a third voltage value at the second terminal of the third transistor is configured to switch between a third high voltage value and a third low voltage value, at least in part based on a second detection voltage value provided by the second voltage divider unit at the first terminal of the third transistor. The second terminal of the third transistor is connected to the first terminal of the first transistor.

10. The circuit of claim 9, wherein, In response to the first voltage detection path and the second voltage detection path being connected to the same voltage to be detected, the second detection voltage value is less than the first detection voltage value.

11. The circuit of claim 9, further comprising a feedback path connected between the second terminal of the first transistor and the first terminal of the third transistor.

12. A circuit comprising: Undervoltage detection path; as well as Overvoltage detection path, The undervoltage detection path includes: First current source; The first voltage divider unit is connected to the first current source; and A first transistor is connected to a first voltage divider unit via a first terminal of the first transistor, and a first voltage value at a second terminal of the first transistor is configured to switch between a first high voltage value and a first low voltage value based at least in part on a first detection voltage value provided by the first voltage divider unit at the first terminal of the first transistor. The overvoltage detection path includes: Second current source; The second voltage divider unit is connected to the second current source; and The second transistor is connected to the second voltage divider unit via a first terminal of the second transistor. The second voltage value at the second terminal of the second transistor is configured to switch between a second high voltage value and a second low voltage value based at least in part on a second detection voltage value provided by the second voltage divider unit at the first terminal of the second transistor. The second terminal of the second transistor is connected to the first terminal of the first transistor.

13. The circuit of claim 12, wherein, The undervoltage detection path and the overvoltage detection path are each connected to the same voltage to be detected. The first detection voltage value is equal to a first ratio of the voltage to be detected, the second detection voltage value is equal to a second ratio of the voltage to be detected, and the first ratio is greater than the second ratio.

14. The circuit of claim 12, wherein, The first voltage divider unit includes a Zener diode, the positive terminal of which is connected to the first terminal of the first transistor.

15. The circuit of claim 14, wherein, The first voltage divider unit includes a first resistor and a second resistor. The first resistor is connected between the first terminal of the first transistor and ground, and the Zener diode is connected in series between the second resistor and the first terminal of the first transistor.

16. The circuit of claim 15, wherein, The first transistor is an NPN bipolar junction transistor, the NPN bipolar junction transistor having a first Vbe with a first temperature coefficient, and the Zener diode having a second temperature coefficient, wherein: Among them, Tempco Vbe The first temperature coefficient, Tempco, represents the first Vbe. Zener R1 represents the resistance of the first resistor, and R2 represents the resistance of the second resistor.

17. The circuit of claim 12, further comprising a feedback path between the second terminal of the first transistor and the first terminal of the second transistor.

18. The circuit of claim 12, further comprising a third transistor, wherein a first terminal of the third transistor is connected to a second terminal of the first transistor. wherein The third voltage at the second terminal of the third transistor is configured to switch between a third high voltage value and a third low voltage value, at least in part based on the first voltage value at the second terminal of the first transistor.

19. The circuit of claim 18, comprising an output stage, the output stage including a comparator, a capacitor, and a diode, wherein: The comparator includes: a first input terminal configured to be connected to a reference voltage; and a second input terminal connected to the first terminal of the capacitor; The negative terminal of the diode is connected to the second terminal of the third transistor, and the positive terminal of the diode is connected to the first terminal of the capacitor; and The first terminal of the capacitor is configured to be connected to a voltage source via a resistor path.

20. A circuit comprising a comparator, a capacitor, and a diode, wherein: The comparator includes: a first input terminal configured to be connected to a reference voltage; and a second input terminal connected to the first terminal of the capacitor; The first terminal of the capacitor is configured to be connected to a voltage source via a resistive path, and the second terminal of the capacitor is connected to ground; and The negative terminal of the diode is configured to be connected to a voltage signal that switches between high and low values, and the positive terminal of the diode is connected to the first terminal of the capacitor.

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