Passive hysteresis current source circuit

Abstract

A passive hysteresis current source circuit includes an high-side switch, a low-side switch, an inductive component, and a controller. The low-side switch is connected to the high-side switch in series on a common node to form an input side. The high-side switch receives an input voltage, and the low-side switch is connected to a ground terminal. The inductive component has a first terminal and a second terminal. The first terminal is connected to the common node, and the second terminal outputs an output current flowing through the inductive component. The controller receives a current voltage signal corresponding to the output current and a reference voltage signal, and compares the current voltage signal with the reference voltage signal. Based on the reference voltage signal being greater than the current voltage signal, the controller turns on the high-side switch and turns off the low-side switch, and based on the reference voltage signal being less than the current voltage signal, the controller turns off the high-side switch and turns on the low-side switch so as to provide the output current with a fixed value.

Description

Technical Field

[0001] This invention relates to a current source circuit, and more particularly to a passive hysteresis current source circuit. Prior Technology

[0002] Buck topologies are commonly used for constant voltage power supplies, but their application in constant current power supplies is rarely discussed.

[0003] However, Figure 1 shows a circuit diagram of a traditional current source circuit. Figure 1 illustrates a current source circuit with a single switch, which uses switch QA and a feedback circuit to achieve a constant current output. However, the traditional single-switch current source circuit suffers from unavoidable power loss because switch QA operates in the ohmic region between full on and full off, resulting in relatively low efficiency.

[0004] Therefore, when using a traditional current source circuit as a current power supply, it requires pulse width modulation (PWM) control technology. This not only necessitates a custom controller design, increasing design complexity and cost, but also limits its performance to specific applications, such as those with a fixed output voltage, making it unsuitable for applications with variable output voltages. Furthermore, PWM control cannot be applied to devices with grounded outputs, such as current loads, significantly restricting its application areas. Moreover, when using a traditional current source circuit as a current load, an external hysteresis circuit is typically required, further increasing design complexity and cost.

[0005] Therefore, how to design a passive hysteresis current source circuit to solve the problems and technical bottlenecks of the existing technology is an important research topic for the inventors of this case. Summary of the Invention

[0006] The purpose of this invention is to provide a passive hysteresis current source circuit. The passive hysteresis current source circuit includes an upper arm switch, a lower arm switch, an inductor, and a controller. The lower arm switch is connected in series with the upper arm switch at a common contact to form the input side. The upper arm switch receives the input voltage, and the lower arm switch is connected to ground. The inductor has a first terminal and a second terminal. The first terminal is connected to the common contact, and the second terminal outputs the output current flowing through the inductor. The controller receives a current-voltage signal corresponding to the output current and a reference voltage signal, and compares the current-voltage signal with the reference voltage signal. When the reference voltage signal is greater than the current-voltage signal, the controller turns on the upper arm switch and turns off the lower arm switch; when the reference voltage signal is less than the current-voltage signal, the controller turns off the upper arm switch and turns on the lower arm switch to provide a constant output current.

[0007] In one embodiment, the upper arm switch has a first terminal, a second terminal, and a control terminal. The lower arm switch also has a first terminal, a second terminal, and a control terminal. The first terminal of the lower arm switch is connected to the second terminal of the upper arm switch at a common contact point, wherein the first terminal of the upper arm switch receives an input voltage, and the second terminal of the lower arm switch is connected to a ground terminal. The second terminal of the inductor and the load terminal form the output side of the current power supply.

[0008] In one embodiment, the upper arm switch has a first terminal, a second terminal, and a control terminal. The lower arm switch has a first terminal, a second terminal, and a control terminal. The first terminal of the lower arm switch is connected to the second terminal of the upper arm switch at a common contact point, wherein the first terminal of the upper arm switch receives an input voltage, and the second terminal of the lower arm switch is connected to a ground terminal. The second terminal of the inductor and the ground terminal form the output side of the current load.

[0009] In one embodiment, the output current can be changed accordingly in response to adjustments in the reference voltage signal.

[0010] In one embodiment, the controller provides an upper arm switch control signal to control the upper arm switch and a lower arm switch control signal to control the lower arm switch.

[0011] In one embodiment, the upper arm switch control signal and the lower arm switch control signal are square wave signals to fully turn on or completely turn off the upper arm switch and the lower arm switch.

[0012] In one embodiment, the upper arm switch control signal and the lower arm switch control signal are level complementary signals.

[0013] In one embodiment, the controller includes a comparator. The comparator has a first input, a second input, and an output. The first input receives a reference voltage signal, and the second input receives a current-voltage signal. After comparing the reference voltage signal and the current-voltage signal, the comparator outputs an upper arm switch control signal and a lower arm switch control signal through its output.

[0014] In one embodiment, the comparator is an operational amplifier.

[0015] In one embodiment, the comparator further includes an inverting unit. The inverting unit is connected to the output of the comparator, receives the upper arm switch control signal, and inverts the level of the upper arm switch control signal to change it into the lower arm switch control signal.

[0016] In one embodiment, the output current increases when the reference voltage signal is greater than the current voltage signal, and decreases when the reference voltage signal is less than the current voltage signal.

[0017] In one embodiment, the inductive element provides hysteretic on and off of the upper arm switch and the lower arm switch.

[0018] In one embodiment, a load is connected to the output side, and the load is connected between the output side and the ground terminal.

[0019] In one embodiment, the output side is directly connected to the ground terminal.

[0020] Therefore, the passive hysteresis current source circuit provided by this invention has the following features and advantages: 1. The passive hysteresis effect can be achieved by using simple passive components and two switches; 2. The passive hysteresis current source circuit of this invention can be used as a current power supply and a current load; 3. The controller circuit structure is simple, mainly relying on comparators and basic logic circuits; 4. Hysteresis control immediately adjusts the switching state according to the current, which is suitable for applications with rapidly changing output current; 5. The energy storage function of the inductor and the stable characteristics of hysteresis control ensure a constant output current; 6. This invention adopts square wave control (rather than pulse width modulation control), so there is no need to use additional means or methods to detect output voltage information, which simplifies the control architecture and reduces costs; 7. The passive hysteresis current source circuit operates in the ohmic region to reduce power loss and improve efficiency.

[0021] To gain a deeper understanding of the techniques, means, and effects employed by this invention to achieve its intended purpose, please refer to the following detailed description and accompanying drawings. It is believed that the purpose, features, and characteristics of this invention can be understood in a thorough and specific manner from these drawings. However, the accompanying drawings are provided for reference and illustration only and are not intended to limit the scope of this invention. Simple Explanation of the Diagram

[0022] Figure 1: Circuit diagram of a traditional current source circuit.

[0023] Figure 2A: is a circuit diagram of the first embodiment of the passive hysteresis current source circuit of the present invention.

[0024] Figure 2B: is a circuit diagram showing the connection of the passive hysteresis current source circuit in Figure 2A to the load.

[0025] Figure 3 is a circuit diagram of the second embodiment of the passive hysteresis current source circuit of the present invention.

[0026] Figure 4: This is a circuit diagram of the controller of the passive hysteresis current source circuit of the present invention.

[0027] Figure 5: This is a schematic waveform diagram of the reference voltage signal, current voltage signal, upper arm switch control signal, output current and input current of the passive hysteresis current source circuit of the present invention. Implementation

[0028] The technical content and detailed description of the present invention are explained below with reference to the accompanying drawings.

[0029] Please refer to Figures 2A, 2B, and 3, which are circuit diagrams of the first and second embodiments of the passive hysteresis current source circuit of the present invention, respectively. Specifically, the first embodiment (Figures 2A and 2B) is used as a current source, meaning it can stably output a fixed current regardless of changes in load impedance. Figure 2B is a circuit diagram showing the passive hysteresis current source circuit of Figure 2A further connected to the powered load. The second embodiment (Figure 3) is used as a current sink, meaning it can stably absorb a fixed current regardless of changes in the drive power supply voltage. Compared to the current source applications shown in Figures 2A and 2B, the current sink application shown in Figure 3 is directly grounded on the output side.

[0030] As shown in Figures 2A, 2B, and / or 3, the passive hysteresis current source circuits 100, 200, and 300 include an upper arm switch QH, a lower arm switch QL, an inductor L, and a controller 10. The upper arm switch QH can also be referred to as a high-side switch; the lower arm switch QL can also be referred to as a low-side switch. The lower arm switch QL is connected in series with the upper arm switch QH at a common contact NC to form the input side IN of the passive hysteresis current source circuits 100, 200, and 300. The upper arm switch QH, located at the input side IN, receives the input voltage VIN, and the lower arm switch QL is connected to the ground terminal GND. In this embodiment, the input voltage VIN can be a DC voltage.

[0031] The inductor L has a first terminal and a second terminal. The first terminal is connected to the common contact NC, and the second terminal outputs the output current IOUT flowing through the inductor L.

[0032] The passive hysteresis current source circuits 100, 200, and 300 are controlled by controller 10. Specifically, controller 10 receives the current-voltage signal VIOUT corresponding to the output current IOUT and the reference voltage signal VREF. In other words, the magnitude of the current-voltage signal VIOUT corresponds to the magnitude of the output current IOUT: the larger the current-voltage signal VIOUT, the larger the output current IOUT; conversely, the smaller the current-voltage signal VIOUT, the smaller the output current IOUT. Therefore, controller 10 can obtain the magnitude of the output current IOUT based on the magnitude of the current-voltage signal VIOUT. Furthermore, controller 10 further compares the current-voltage signal VIOUT with the reference voltage signal VREF.

[0033] To further explain, based on the reference voltage signal VREF being greater than the current voltage signal VIOUT, the controller 10 turns on the upper arm switch QH and turns off the lower arm switch QL, and based on the reference voltage signal VREF being less than the current voltage signal VIOUT, the controller 10 turns off the upper arm switch QH and turns on the lower arm switch QL to provide a constant output current IOUT.

[0034] As shown in Figures 2A, 2B, and / or 3, the upper arm switch QH has a first terminal, a second terminal, and a control terminal. The lower arm switch QL has a first terminal, a second terminal, and a control terminal. The first terminal of the lower arm switch QL is connected to the second terminal of the upper arm switch QH at a common contact NC. The first terminal of the upper arm switch QH receives the input voltage VIN, and the second terminal of the lower arm switch QL is connected to the ground terminal GND.

[0035] For the current power supplies shown in Figures 2A and 2B, the first end of the inductor L is connected to the common contact NC, and the second end of the inductor L and the load terminal form the output side OUT of the current power supply. The load terminal refers to the endpoint used to connect the load. Compared to Figure 2A, Figure 2B further shows a load R connected between the output side OUT and the ground terminal GND.

[0036] For the current load in Figure 3, the first end of the inductor L is connected to the common terminal NC, and the second end of the inductor L and the ground terminal GND form the output side OUT of the current load, that is, the output side OUT is directly connected to the ground terminal GND.

[0037] Incidentally, the controller 10 provides an upper arm switch control signal SQH to control the upper arm switch QH, and provides a lower arm switch control signal SQL to control the lower arm switch QL. The upper arm switch control signal SQH and the lower arm switch control signal SQL are complementary signals in terms of level. That is, when the upper arm switch control signal SQH is at a high level, the lower arm switch control signal SQL is at a low level; conversely, when the upper arm switch control signal SQH is at a low level, the lower arm switch control signal SQL is at a high level.

[0038] As shown in Figures 2A, 2B, and / or 3, the passive hysteresis current source circuits 100, 200, and 300 of this invention are essentially buck converters. However, unlike existing power converters that control switching elements using pulse-width modulation (PWM), this invention uses a triangular or sawtooth wave as a carrier wave, compared with a reference wave to generate control signals for the switching elements. In this invention, the upper arm switch control signal SQH and the lower arm switch control signal SQL provided by the controller 10 are square wave signals. That is, this invention uses linear control of square wave signals to fully turn on or off the upper arm switch control signal SQH and the lower arm switch control signal SQL, ensuring that the upper arm switch QH and the lower arm switch QL can be fully turned on or off, thus ensuring normal and correct operation. Incidentally, since pulse width modulation control requires information about the output voltage to function, this invention uses linear control of a square wave signal (rather than pulse width modulation control) to eliminate the need for additional means or methods to detect the output voltage information, thus simplifying the circuit's control architecture and reducing costs.

[0039] Please refer to Figure 4, which is a circuit diagram of the controller of the passive hysteresis current source circuit of the present invention. The controller 10 includes a comparator 11 and an inverting unit 12. The comparator 11 has a first input terminal, a second input terminal, and an output terminal. In this embodiment, the first input terminal receives a reference voltage signal VREF, and the second input terminal receives a current voltage signal VIOUT, but this is not intended to limit the present invention. After comparing the reference voltage signal VREF and the current voltage signal VIOUT, the comparator 11 outputs the upper arm switch control signal SQH and the lower arm switch control signal SQL through the output terminal.

[0040] In this embodiment, comparator 11 is an operational amplifier, with its first input being a non-inverting input and its second input being an inverting input. Therefore, the non-inverting input receives the reference voltage signal VREF, and the inverting input receives the current-voltage signal VIOUT. After the operational amplifier compares the reference voltage signal VREF with the current-voltage signal VIOUT, it outputs the upper arm switch control signal SQH. Furthermore, the inverting unit 12 is connected to the output of comparator 11, receives the upper arm switch control signal SQH, and inverts the level of the upper arm switch control signal SQH to change it to the lower arm switch control signal SQL. That is, when the upper arm switch control signal SQH is at a high level, after passing through the inverting unit 12, the lower arm switch control signal SQL is at a low level; conversely, when the upper arm switch control signal SQH is at a low level, after passing through the inverting unit 12, the lower arm switch control signal SQL is at a high level. However, the description of comparator 11 and inverting unit 12 above is only one implementation. Therefore, the output of comparator 11 can also be used as the lower arm switch control signal SQL, and after passing through inverting unit 12, it generates the upper arm switch control signal SQH.

[0041] As previously stated, the upper arm switch QH and lower arm switch QL, provided by controller 10, control the complete on / off state of the upper arm switch QH and lower arm switch QL, respectively, thereby enabling the passive hysteresis current source circuits 100, 200, and 300 to provide a constant output current IOUT. Therefore, when the reference voltage signal VREF is greater than the current voltage signal VIOUT, the upper arm switch QH is on and the lower arm switch QL is off, resulting in an increase in the current flowing through the inductor L, and thus an increase in the output current IOUT. Conversely, when the reference voltage signal VREF is less than the current voltage signal VIOUT, the upper arm switch QH is off and the lower arm switch QL is on, resulting in a decrease in the current flowing through the inductor L, and thus a decrease in the output current IOUT.

[0042] Therefore, once the set reference voltage signal VREF is fixed, the controller 10 will control one of the upper arm switch QH and the lower arm switch QL to be fully turned on and the other to be fully turned off, based on the comparison result between the reference voltage signal VREF and the current voltage signal VIOUT, thereby adjusting the output current IOUT to increase or decrease, and thus achieving a constant output current IOUT.

[0043] It is worth mentioning that, if the passive hysteresis current source circuits 100 and 200 (which are current power supplies) shown in Figures 2A and 2B are to output a varying output current IOUT, the magnitude of the reference voltage signal VREF can be adjusted to correspondingly change the output current IOUT to a constant magnitude. For example, if the passive hysteresis current source circuit 100 wants to provide a larger constant output current IOUT, the reference voltage signal VREF can be increased, and based on the comparison result between the aforementioned reference voltage signal VREF and the current voltage signal VIOUT, one of the upper arm switch QH and the lower arm switch QL can be fully turned on and the other fully turned off, thereby adjusting the output current IOUT to achieve a constant output current IOUT.

[0044] Furthermore, if the passive hysteresis current source circuit 300 (a current load device) shown in Figure 3 wants to absorb (pump) a fluctuating output current IOUT, it can adjust the magnitude of the reference voltage signal VEREF, thereby changing the output current IOUT to a constant value. For example, if the passive hysteresis current source circuit 200 wants to provide a larger constant output current IOUT, it can increase the reference voltage signal VEREF, and based on the comparison result between the aforementioned reference voltage signal VEREF and the current voltage signal VEREF, control one of the upper arm switch QH and the lower arm switch QL to be fully turned on and the other to be fully turned off, thereby adjusting the output current IOUT to achieve a constant output current IOUT.

[0045] Please refer to Figure 5, which is a schematic waveform diagram of the reference voltage signal, current voltage signal, upper arm switch control signal, output current, and input current of the passive hysteresis current source circuit of the present invention. As shown in Figure 5, the first column shows the waveform diagram of the reference voltage signal VREF and the current voltage signal VIOUT; the second column shows the waveform diagram of the upper arm switch control signal SQH; the third column shows the waveform diagram of the output current IOUT; and the fourth column shows the waveform diagram of the input current IIN. Referring to the above description, during time t1 to time t2, assuming the reference voltage signal VREF is set to 2.70 volts (but not limited to this), the comparator 11 of the controller 10 will compare the reference voltage signal VREF with the current voltage signal VIOUT. If the reference voltage signal VREF is greater than the current voltage signal VIOUT, the upper arm switch QH is turned on and the lower arm switch QL is turned off, thus increasing the current flowing through the inductor L (because the inductor L is charging), and therefore increasing the output current IOUT. Conversely, if the reference voltage signal VREF is less than the current voltage signal VIOUT, the upper arm switch QH is turned off and the lower arm switch QL is turned on, thus decreasing the current flowing through the inductor L (because the inductor L is discharging), and therefore decreasing the output current IOUT. In this way, the upper arm switch QH and the lower arm switch QL are alternately turned on and off to form a periodic switching, so as to achieve a constant output current IOUT, that is, to ensure that the output current IOUT fluctuates around the target current value without deviating from the hysteresis range (i.e., the hysteresis range limits the amplitude of the current fluctuation), which is about 30 amps in this embodiment.

[0046] Furthermore, to meet the demand for a larger output current IOUT from the passive hysteresis current source circuits 100 and 200 (current power supplies), or to meet the demand for a larger output current IOUT from the passive hysteresis current source circuit 300 (current load), at time t2, when the reference voltage signal VREF is adjusted to a larger 3.00 volts, the controller 10 will continuously output a high-level upper arm switch control signal SQH to control the upper arm switch QH to remain on, thus gradually increasing the output current IOUT. At this time, the current voltage signal VIOUT will also increase accordingly until a constant output current IOUT is reached, which is approximately 60 amperes in this embodiment. The operation of the controller 10 during this process can be found in the preceding description and will not be repeated here.

[0047] Similarly, if the passive hysteresis current source circuits 100 and 200 (current power supply units) require a smaller output current IOUT, or if the passive hysteresis current source circuit 300 (current load unit) requires a smaller output current IOUT, then at time t3, when the reference voltage signal VREF is adjusted back to a smaller 2.70 volts, the controller 10 will continuously output a low-level upper arm switch control signal SQH to control the upper arm switch QH to remain continuously off, thus gradually reducing the output current IOUT. At this time, the current voltage signal VIOUT will also decrease accordingly until a constant output current IOUT is reached, which in this embodiment is approximately 30 amperes. The operation of the controller 10 during this process can be found in the preceding description and will not be repeated here.

[0048] However, the constant current of 30 amps or 60 amps mentioned above is not intended to limit the present invention. It can be adjusted and set according to the magnitude of the current to be output by the passive hysteresis current source circuit 100, 200 (which is a current power supply) or the magnitude of the current to be drawn by the passive hysteresis current source circuit 300 (which is a current load) (i.e., the dynamic current needs to be constant) in order to achieve the purpose of constant output current IOUT.

[0049] Incidentally, due to the limitations of the switching elements, they cannot be fully turned on and off at high speeds (e.g., microseconds, nanoseconds). Therefore, to ensure that the upper arm switch QH and the lower arm switch QL can operate under normal on and off conditions (rather than operating in the ohmic region between full on and full off), this invention utilizes the transient response capability of the inductor L to current to provide hysteretic on and off of the upper arm switch QH and the lower arm switch QL, thereby reducing power loss and improving efficiency.

[0050] Incidentally, when the passive hysteresis current source circuit 200 is used as a current power supply, it can be used with a diode (not shown in the figure). The diode is located between the output side OUT of the passive hysteresis current source circuit 200 and the ground terminal GND, that is, between the inductor L and the ground terminal GND, to enable the current power supply to provide a stable output current IOUT.

[0051] In summary, the passive hysteresis current source circuit provided by this invention has the following features and advantages:

[0052] 1. By using simple passive components and two switches, the effect of passive hysteresis can be achieved.

[0053] 2. The passive hysteresis current source circuit of the present invention can be used as a current power supply and a current load.

[0054] 3. The controller has a simple circuit structure, mainly relying on comparators and basic logic circuits.

[0055] 4. Hysteresis control adjusts the switching state immediately according to the current current, which is suitable for applications where the output current changes rapidly.

[0056] 5. The energy storage function of the inductor and the stability characteristics of hysteresis control ensure a constant output current.

[0057] 6. This invention uses linear control of square wave signals (rather than pulse width modulation control), so there is no need to use additional means or methods to detect output voltage information, which simplifies the control architecture and cost of the circuit.

[0058] 7. The passive hysteresis current source circuit operates in the ohmic region to reduce power loss and improve efficiency.

[0059] The above description is merely a detailed explanation and illustration of preferred embodiments of the present invention. However, the features of the present invention are not limited thereto and are not intended to limit the present invention. The scope of the present invention should be determined by the following claims. All embodiments that conform to the spirit of the claims and similar variations thereof should be included in the scope of the present invention. Any variations or modifications that can be easily conceived by those skilled in the art within the field of the present invention can be covered by the following claims.

[0060] 100, 200, 300: Passive hysteresis current source circuit 10: Controller 11: Comparator 12: Inverting unit QH: Upper arm switch QL: Lower arm switch L: Inductor element R: Load IN: Input side OUT: Output side I OUT: Output current IIN: Input current VIN: Input voltage NC: Common contact GND: Ground terminal V IOUT: Current and voltage signals V REF: Reference voltage signal S QH: Upper arm switch control signal SQL: Lower arm switch control signal t1, t2, t3: Time QA: Switch

Claims

1. A passive hysteresis current source circuit, comprising: An upper arm switch; a lower arm switch, connected in series with the upper arm switch to a common contact to form an input side, wherein the upper arm switch receives an input voltage and the lower arm switch is connected to a ground terminal; an inductor having a first terminal and a second terminal, the first terminal being connected to the common contact and the second terminal outputting an output current flowing through the inductor; and a controller receiving a current-voltage signal corresponding to the output current and a reference voltage signal, and comparing the current-voltage signal with the reference voltage signal; wherein if the reference voltage signal is greater than the current-voltage signal, the controller turns on the upper arm switch and turns off the lower arm switch, and if the reference voltage signal is less than the current-voltage signal, the controller turns off the upper arm switch and turns on the lower arm switch to provide a constant output current.

2. The passive hysteresis current source circuit as described in claim 1, wherein the upper arm switch has a first terminal, a second terminal and a control terminal; the lower arm switch has a first terminal, a second terminal and a control terminal, the first terminal of the lower arm switch is connected to the second terminal of the upper arm switch at the common contact point, wherein the first terminal of the upper arm switch receives the input voltage and the second terminal of the lower arm switch is connected to the ground terminal; and the second terminal of the inductor and a load terminal form an output side of a current power supply.

3. The passive hysteresis current source circuit as described in claim 1, wherein the upper arm switch has a first terminal, a second terminal and a control terminal; the lower arm switch has a first terminal, a second terminal and a control terminal, the first terminal of the lower arm switch is connected to the second terminal of the upper arm switch at the common contact point, wherein the first terminal of the upper arm switch receives the input voltage and the second terminal of the lower arm switch is connected to the ground terminal; and the second terminal of the inductor and a ground terminal form an output side of a current load.

4. The passive hysteresis current source circuit as described in claim 1, wherein the output current can be changed accordingly in response to the adjustment of the reference voltage signal.

5. The passive hysteresis current source circuit as described in claim 1, wherein the controller provides an upper arm switch control signal to control the upper arm switch and provides a lower arm switch control signal to control the lower arm switch.

6. The passive hysteresis current source circuit as described in claim 5, wherein the upper arm switch control signal and the lower arm switch control signal are square wave signals to fully turn on or completely turn off the upper arm switch and the lower arm switch.

7. The passive hysteresis current source circuit as described in claim 5, wherein the upper arm switch control signal and the lower arm switch control signal are level complementary signals.

8. The passive hysteresis current source circuit as described in claim 5, wherein the controller comprises: A comparator having a first input terminal, a second input terminal, and an output terminal; The first input terminal receives the reference voltage signal, and the second input terminal receives the current voltage signal; wherein the comparator compares the reference voltage signal and the current voltage signal, and then outputs the upper arm switch control signal and the lower arm switch control signal through the output terminal.

9. The passive hysteresis current source circuit as described in claim 8, wherein the comparator is an operational amplifier.

10. The passive hysteresis current source circuit as described in claim 8, wherein the comparator further comprises: An inverting unit is connected to the output terminal of the comparator, receives the upper arm switch control signal, and inverts the level of the upper arm switch control signal to change it into the lower arm switch control signal.

11. The passive hysteresis current source circuit as claimed in claim 1, wherein the output current increases when the reference voltage signal is greater than the current voltage signal, and decreases when the reference voltage signal is less than the current voltage signal.

12. The passive hysteresis current source circuit as described in claim 1, wherein the inductive element provides hysteretic on and off of the upper arm switch and the lower arm switch.

13. The passive hysteresis current source circuit as described in claim 2, wherein a load is connected to the output side, and the load is connected between the output side and the ground terminal.

14. The passive hysteresis current source circuit as described in claim 3, wherein the output side is directly connected to the ground terminal.

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