Anti-spike pulse circuit and mower

Abstract

The utility model discloses an anti-spike pulse circuit and a mower, the circuit comprises a starting circuit, a filter circuit, a modulation frequency circuit, a current sampling comparison circuit, an error comparator circuit, a control chip UC3845B and an MOS transistor, the starting circuit is connected with a seventh pin of the control chip UC3845B, the filter circuit is connected with a seventh pin of the control chip UC3845B, and the MOS transistor is connected with the control chip UC3845B. The modulation frequency circuit is connected with a fourth pin and an eighth pin of the control chip UC3845B, the error comparator circuit is connected with a second pin of the control chip UC3845B, and the MOS tube is connected with a sixth pin of the control chip UC3845B. The utility model has the characteristics of wide input voltage range, high output voltage precision and high load adjustment efficiency, so as to solve the problem of spike pulse generated by the walking motor of the hybrid power mower.

Description

Technical Field

[0001] The utility model relates to the technical field of power supply, in particular to an engine anti-peak pulse circuit and a lawn mower for hybrid power. Background Art

[0002] When the travel motor of an electric tool is working, a spike pulse will be generated due to the sudden change of the rotor magnetic flux. A spike pulse is a phenomenon in which the current or voltage suddenly changes in a short period of time, and its width is generally at the microsecond level. This phenomenon may damage the performance of the equipment.

[0003] The existing anti-spike pulse circuit adopts a flyback switching power supply. The flyback switching power supply is widely used in the power supply of automatic control and intelligent instruments due to its advantages of simple structure and few components. The regulating part of the switching power supply usually adopts pulse width modulation (PWM) technology, that is, when the main converter cycle remains unchanged, the duty cycle of the power MOSFET tube is adjusted according to the change of input voltage or load, so as to stabilize the output voltage. There are many methods of pulse width modulation. The pulse width modulation method in the prior art has a narrow input voltage range, low output voltage accuracy, and low load modulation efficiency. Therefore, there is an urgent need for an anti-spike pulse circuit for hybrid power mowers with a wide input voltage range, high output voltage accuracy, and high load adjustment efficiency. Utility Model Content

[0004] In view of the above technical problems, the utility model provides an anti-spike pulse circuit for a hybrid power lawn mower to solve the problem of spike pulses generated by a travel motor of the hybrid power lawn mower.

[0005] An embodiment of the utility model provides an anti-spike pulse circuit, the circuit comprising a startup circuit, a filter circuit, a modulation frequency circuit, a current sampling comparison circuit, an error comparator circuit, a control chip UC3845B and a MOS tube, the startup circuit is connected to the seventh pin of the control chip UC3845B, the filter circuit is connected to the seventh pin of the control chip UC3845B, the modulation frequency circuit is connected to the fourth pin and the eighth pin of the control chip UC3845B, the error comparator circuit is connected to the second pin of the control chip UC3845B, and the MOS tube is connected to the sixth pin of the control chip UC3845B.

[0006] Optionally, the filter circuit includes a filter capacitor, one end of the filter capacitor is grounded, and the other end is respectively connected to the start-up circuit and the seventh pin of the control chip UC3845B.

[0007] Optionally, the starting circuit includes a first diode, a second diode and a first capacitor, the cathode of the first diode is connected to the filter capacitor, the positive electrode of the first diode is respectively connected to the positive electrode of the first capacitor and the negative electrode of the second diode, the positive electrode of the second diode is connected to the power supply, and the negative electrode of the first capacitor is grounded.

[0008] Optionally, the modulation frequency circuit includes a second capacitor, a first resistor and a third capacitor, the positive electrode of the second capacitor is connected to the fourth pin of the control chip UC3845B, and the negative electrode thereof is grounded, the positive electrode of the second capacitor is respectively connected to the positive electrode of the third capacitor and the eighth pin of the control chip UC3845B through the first resistor, and the negative electrode of the third capacitor is grounded.

[0009] Optionally, the current sampling and comparison circuit includes a fourth capacitor, a second resistor and a third resistor, the positive electrode of the fourth capacitor is respectively connected to the third pin of the control chip UC3845B and one end of the second resistor, the negative electrode of the fourth capacitor is grounded, the other end of the second resistor is respectively connected to one end of the third resistor and the source of the MOS tube, and the gate of the MOS tube is connected to the sixth pin of the control chip UC3845B.

[0010] Optionally, the error comparator circuit includes a fifth capacitor, a fourth resistor and a fifth resistor, one end of the fifth capacitor is respectively connected to one end of the fourth resistor, one end of the fifth resistor and the second pin of the control chip UC3845B, the other end of the fifth capacitor is connected to the other end of the fourth resistor and the first pin of the control chip UC3845B, and the other end of the fifth resistor is grounded.

[0011] Optionally, the circuit further includes a transformer, and one side of the transformer is connected to the seventh pin of the control chip UC3845B through a third diode and a fourth diode.

[0012] Optionally, the circuit also includes a sixth capacitor, a seventh capacitor and a sixth resistor, the positive electrode of the third diode is connected to one side of the transformer, the negative electrode of the third diode is connected to the positive electrode of the sixth capacitor, the negative electrode of the sixth capacitor is connected to one side of the transformer, one end of the sixth resistor is respectively connected to the negative electrode of the third diode, the positive electrode of the sixth capacitor and the positive electrode of the fourth diode, the other end of the sixth resistor is respectively connected to the negative electrode of the sixth capacitor and the negative electrode of the seventh capacitor, and the positive electrode of the seventh capacitor is connected to the seventh pin of the control chip UC3845B and the filter capacitor.

[0013] Optionally, the circuit is applied to a lawn mower.

[0014] The utility model also provides a lawn mower, comprising an engine and a motor, and also comprising the above-mentioned anti-peak pulse circuit.

[0015] In the technical solution provided by the embodiment of the utility model, the starting circuit is connected to the seventh pin of the control chip UC3845B, the filtering circuit is connected to the seventh pin of the control chip UC3845B, the modulation frequency circuit is connected to the fourth pin and the eighth pin of the control chip UC3845B, the error comparator circuit is connected to the second pin of the control chip UC3845B, and the MOS tube is connected to the sixth pin of the control chip UC3845B. Compared with the prior art, the utility model has the characteristics of wide input voltage range, high output voltage accuracy and high load adjustment efficiency, so as to solve the problem of peak pulses generated by the travel motor of the hybrid power lawn mower. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The utility model is a circuit diagram of an anti-spike pulse circuit. DETAILED DESCRIPTION

[0017] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the utility model.

[0018] It should be noted that when an element is described as being "connected" or "connected to" another element, it may be directly connected to the other element, or one or more intermediate elements may exist therebetween. The terms "upper", "lower", "inner", "outer", etc. used in this specification indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as a limitation on the present invention.

[0019] The utility model provides a spike pulse protection circuit, please refer to Figure 1 As shown, the circuit includes a starting circuit 10, a filtering circuit 20, a modulation frequency circuit 30, a current sampling comparison circuit 50, an error comparator circuit 60, a control chip UC3845B and a MOS tube 70. The starting circuit 10 is connected to the seventh pin of the control chip UC3845B, the filtering circuit 20 is connected to the seventh pin of the control chip UC3845B, the modulation frequency circuit 30 is connected to the fourth pin and the eighth pin of the control chip UC3845B, the error comparator circuit 60 is connected to the second pin of the control chip UC3845B, and the MOS tube 70 is connected to the sixth pin of the control chip UC3845B.

[0020] The control chip UC3845B described in the utility model is a high-performance fixed-frequency current-type pulse width integrated control chip. The chip has the characteristics of an internal oscillator, a high-precision error comparator, cycle-by-cycle current sampling comparison, a small startup circuit, and a large current totem pole output, and is an ideal device for driving MOS tubes.

[0021] The filter circuit 20 includes a filter capacitor, one end of which is grounded, and the other end is connected to the startup circuit 10 and the seventh pin of the control chip UC3845B, respectively. The filter capacitor is also connected to the error comparator circuit 60 through an 18K resistor. When the filter circuit 20 is started, in order to filter out the high-frequency signal at the power supply end, a ceramic capacitor, namely the seventh capacitor C7, is connected to the ground of VCC.

[0022] The startup circuit 10 includes a first diode D1, a second diode D2 and a first capacitor C1, wherein the cathode of the first diode D1 is connected to the filter capacitor, the anode of the first diode D1 is connected to the anode of the first capacitor C1 and the cathode of the second diode D2, respectively, the anode of the second diode D2 is connected to the power supply, and the cathode of the first capacitor C1 is grounded. When the DC input voltage of the startup circuit 10 is greater than 40V, the control chip UC3845B starts to work.

[0023] The modulation frequency circuit 30 includes a second capacitor C2, a first resistor R1 and a third capacitor C3, wherein the positive electrode of the second capacitor C2 is connected to the fourth pin of the control chip UC3845B, and the negative electrode thereof is grounded, and the positive electrode of the second capacitor C2 is respectively connected to the positive electrode of the third capacitor C3 and the eighth pin of the control chip UC3845B through the first resistor R1, and the negative electrode of the third capacitor C3 is grounded. When the oscillator of the modulation frequency circuit 30 is charged, the latch sets the input square wave to a low level, and when it is discharged, the input square wave is a high level.

[0024] The current sampling comparison circuit 50 includes a fourth capacitor C4, a second resistor R2 and a third resistor R3. The positive electrode of the fourth capacitor C4 is connected to the third pin of the control chip UC3845B and one end of the second resistor R2, respectively. The negative electrode of the fourth capacitor C4 is grounded. The other end of the second resistor R2 is connected to one end of the third resistor R3 and the source of the MOS tube 70, respectively. The gate of the MOS tube 70 is connected to the sixth pin of the control chip UC3845B. The current sampling comparison circuit 50 transmits the sampled voltage to the third pin of the control chip UC3845B after RC filtering. When the voltage exceeds 1V, the comparator outputs a high level and sends it to the reset end of the RS latch. The PWM output is a low level, which reduces the duty cycle of the PWM, thereby limiting the peak current of the inductor.

[0025] The error comparator circuit 60 includes a fifth capacitor C5, a fourth resistor R4 and a fifth resistor R5, one end of the fifth capacitor C5 is respectively connected to one end of the fourth resistor R4, one end of the fifth resistor R5 and the second pin of the control chip UC3845B, the other end of the fifth capacitor C5 is connected to the other end of the fourth resistor R4 and the first pin of the control chip UC3845B, and the other end of the fifth resistor R5 is grounded.

[0026] The second pin of the external monitoring voltage input control chip UC3845B of the error comparator circuit 60 can be used to introduce a voltage feedback link into the output loop. When the output loop voltage rises due to some reason, the external monitoring voltage input terminal is greater than 2.5V, the error comparator output is less than 2.5V, and the input voltage is compared with the current sampling. The PWM output is low level, which reduces the PWM duty cycle and the output loop voltage.

[0027] The circuit further includes a transformer, one side of which is connected to the seventh pin of the control chip UC3845B via a third diode D3 and a fourth diode D4.

[0028] The circuit also includes a sixth capacitor C6, a seventh capacitor C7 and a sixth resistor R6, the positive electrode of the third diode D3 is connected to one side of the transformer, the negative electrode of the third diode D3 is connected to the positive electrode of the sixth capacitor C6, the negative electrode of the sixth capacitor C6 is connected to one side of the transformer, one end of the sixth resistor R6 is respectively connected to the negative electrode of the third diode D3, the positive electrode of the sixth capacitor C6 and the positive electrode of the fourth diode D4, the other end of the sixth resistor R6 is respectively connected to the negative electrode of the sixth capacitor C6 and the negative electrode of the seventh capacitor C7, and the positive electrode of the seventh capacitor C7 is connected to the seventh pin of the control chip UC3845B and the filter capacitor.

[0029] When the DC input voltage is greater than 40V, the control chip UC3845B starts to work. After the startup process is completed, the current consumption of the control chip UC3845B will increase to about 100mA as the MOS tube 70 is turned on. At this time, the voltage on the start capacitor will drop to more than 7.6V. To keep the control chip UC3845B working, the transformer feedback winding should be able to provide the feed voltage in time. The filter circuit is to filter out the high-frequency signal at the power supply end. The frequency of the oscillator OSC is determined by the selected values ​​of the timing elements RT and CT. When the MOS tube is turned on, the transformer inductor current increases linearly with a slope. A non-inductive sampling resistor is connected in series between the source and ground of the MOS tube to convert the primary current of the transformer into a sampling voltage. Under the same output power, the smaller the input DC voltage, the larger the primary current of the transformer, and the larger the current passing through the MOS tube. VCC is connected to the monitoring voltage input terminal through a resistor divider. When the output circuit voltage increases for some reason, the external monitoring voltage input terminal is greater than 2.5V, the error comparator output is less than 2.5V, and the input voltage is compared with the current sampling. The PWM output is low level, which reduces the PWM duty cycle and the output circuit voltage.

[0030] The anti-spike pulse circuit described in the utility model is applied to a hybrid power lawn mower. The utility model is an anti-spike pulse circuit based on the control chip UC3845B, which has the characteristics of wide input voltage range, high output voltage accuracy, high load adjustment efficiency, etc., to solve the problem of spike pulses generated by the travel motor of the hybrid power lawn mower.

[0031] The utility model further provides a lawn mower, which comprises an engine and a motor, and also comprises the anti-spike pulse circuit described in any one of the above embodiments.

[0032] In the several embodiments provided in the present application, it should be understood that the circuit or device embodiments described above are merely illustrative. In addition, the connections, direct connections, or communication connections between the components shown or discussed may be through some interfaces, indirect couplings or communication connections of devices or units, which may be electrical, mechanical, or other forms.

[0033] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A spike protection circuit, characterized in that: The circuit includes a startup circuit, a filter circuit, a modulation frequency circuit, a current sampling comparison circuit, an error comparator circuit, a control chip UC3845B and a MOS tube. The startup circuit is connected to the seventh pin of the control chip UC3845B, the filter circuit is connected to the seventh pin of the control chip UC3845B, the modulation frequency circuit is connected to the fourth pin and the eighth pin of the control chip UC3845B, the error comparator circuit is connected to the second pin of the control chip UC3845B, and the MOS tube is connected to the sixth pin of the control chip UC3845B.

2. The spike protection circuit according to claim 1, characterized in that: The filter circuit comprises a filter capacitor, one end of which is grounded, and the other end of which is respectively connected to the start-up circuit and the seventh pin of the control chip UC3845B.

3. The spike protection circuit according to claim 2, characterized in that: The starting circuit includes a first diode, a second diode and a first capacitor, the cathode of the first diode is connected to the filter capacitor, the anode of the first diode is respectively connected to the anode of the first capacitor and the cathode of the second diode, the anode of the second diode is connected to a power supply, and the cathode of the first capacitor is grounded.

4. The spike protection circuit according to claim 1, characterized in that: The modulation frequency circuit includes a second capacitor, a first resistor and a third capacitor, the positive electrode of the second capacitor is connected to the fourth pin of the control chip UC3845B, and the negative electrode thereof is grounded, the positive electrode of the second capacitor is respectively connected to the positive electrode of the third capacitor and the eighth pin of the control chip UC3845B through the first resistor, and the negative electrode of the third capacitor is grounded.

5. The spike protection circuit according to claim 1, characterized in that: The current sampling and comparison circuit includes a fourth capacitor, a second resistor and a third resistor. The positive electrode of the fourth capacitor is respectively connected to the third pin of the control chip UC3845B and one end of the second resistor, the negative electrode of the fourth capacitor is grounded, the other end of the second resistor is respectively connected to one end of the third resistor and the source of the MOS tube, and the gate of the MOS tube is connected to the sixth pin of the control chip UC3845B.

6. The spike protection circuit according to claim 1, characterized in that: The error comparator circuit includes a fifth capacitor, a fourth resistor and a fifth resistor, one end of the fifth capacitor is respectively connected to one end of the fourth resistor, one end of the fifth resistor and the second pin of the control chip UC3845B, the other end of the fifth capacitor is connected to the other end of the fourth resistor and the first pin of the control chip UC3845B, and the other end of the fifth resistor is grounded.

7. The spike protection circuit according to claim 1, characterized in that: The circuit further includes a transformer, one side of which is connected to the seventh pin of the control chip UC3845B via a third diode and a fourth diode.

8. The spike protection circuit according to claim 7, characterized in that: The circuit also includes a sixth capacitor, a seventh capacitor and a sixth resistor. The positive electrode of the third diode is connected to one side of the transformer, the negative electrode of the third diode is connected to the positive electrode of the sixth capacitor, the negative electrode of the sixth capacitor is connected to one side of the transformer, one end of the sixth resistor is respectively connected to the negative electrode of the third diode, the positive electrode of the sixth capacitor and the positive electrode of the fourth diode, the other end of the sixth resistor is respectively connected to the negative electrode of the sixth capacitor and the negative electrode of the seventh capacitor, and the positive electrode of the seventh capacitor is connected to the seventh pin of the control chip UC3845B and the filter capacitor.

9. The spike protection circuit according to claim 1, characterized in that: The circuit is applied to a lawn mower.

10. A lawn mower, comprising an engine and a motor, characterized in that: It also includes the anti-spike pulse circuit according to any one of claims 1-9.

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