Insulation detection circuit and method thereof

An insulation detection circuit suitable for detecting an insulation status between a high voltage power and a low voltage power of a vehicle is disclosed. The circuit includes a first energy storage unit, a second energy storage unit, a constant current unit, and a detection unit. The first energy storage unit is coupled to the high voltage power. The second energy storage unit is coupled between the first energy storage unit and the low voltage power. The constant current unit is coupled between the first energy storage unit and the second energy storage unit. The detection unit is coupled to the second energy storage unit for detecting a current change of the second energy storage unit. When the detection unit detects that current flowing through the second energy storage unit is smaller than a predetermined value, a detection signal representing that the insulation status is abnormal is outputted.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present disclosure relates to an insulation detection circuit and method thereof; in particular, to an insulation detection circuit and method thereof which are applied between a high voltage power and a low voltage power of a vehicle.

2. Description of Related Art

According to the progress of the technology, the transportation vehicle is provided with versatile electric instruments such as the illumination lights, the electromotive windows, the digital video/audios, the navigation systems, or the isothermal air conditioners, etc. Those electric instruments are operated by using the power supplied from the battery, the electricity generator, or the high voltage to low voltage converter. Of course, there needs a good insulation between the high voltage power and the low voltage power of the vehicle, for making people use versatile electric instruments safely.

However, the progression of the vehicle goes toward the hybrid vehicles or electric vehicles of green energy industry, and the electric vehicle may output a high voltage of about 60 to 600 volts by means of, for example, a driving chain including the high voltage battery and the high voltage to low voltage converter. However, the high voltage exceeding 60 volts is considered to be harmful to people.

When the insulation between the high voltage power and the low voltage power of the vehicle is damaged, the current may leak to the chassis or the shell of the vehicle, thus the chassis or the shell of the vehicle may contain the charges which are harmful to human body. If the user touches any part of the chassis or shell of the vehicle, the user may be hurted by electric shocks.

For example, when the vehicle is subject to strong vibrations, thus the insulation body is abraded or cracked mechanically, such as the insulation body damage of the high voltage cable of the vehicle. Thus, the current of the high voltage power may leak to the shell of the vehicle. For warning the user, driver, and passenger of the vehicle about the leakage current caused by the damaged insulation body, the vehicle needs to be installed with the insulation detection circuits for detecting the condition of damaged insulation which may happen.

Therefore, the abnormal insulation status between the high voltage power and the low voltage power of the vehicle is a serious problem which needs to be detected, for ensuring the safety of the people who may touch the vehicle. Thus, how to improve the accuracy of the insulation detection circuits during operation is an important topic.

SUMMARY OF THE INVENTION

The present disclosure provides an insulation detection circuit. The circuit uses a constant current unit to provide a stable constant current for charging/discharging a second energy storage unit, and when the current of the second energy storage unit is smaller than a predetermined value, a detection unit may precisely detect that the insulation between the high voltage power and the low voltage power of the vehicle is damaged. Therefore, the present disclosure can enhance the usage convenience of the insulation detection circuit.

The present disclosure provides an insulation detection circuit suitable for detecting an insulation status between a high voltage power and a low voltage power of a vehicle. The insulation detection circuit includes a first energy storage unit, a second energy storage unit, a constant current unit, and a detection unit. The first energy storage unit is coupled to a high voltage power. The second energy storage unit is coupled between the first energy storage unit and a low voltage power. The constant current unit is coupled between the first energy storage unit and the second energy storage unit, and provides a constant current for charging/discharging the second storage unit. The detection unit is coupled to the second energy storage unit for detecting a current change of the second energy storage unit. When the detection unit detects that the current flowing through the second energy storage unit is smaller than a predetermined value, the detection unit then outputs a detection signal representing that the insulation status is abnormal.

The present disclosure provides an insulation detection method suitable for detecting an insulation status between a high voltage power and a low voltage power of a vehicle. The insulation detection method includes: providing a first energy storage unit coupled to the high voltage power; providing a second energy storage unit coupled between the first energy storage unit and a low voltage power; providing a constant current for charging/discharging the second energy storage unit; detecting a current change of the current flowing through the second energy storage unit; and when detecting that the current flowing through the second energy storage unit is smaller than a predetermined value, a detection signal representing the abnormity of the insulation status is outputted.

The present disclosure provides an insulation detection circuit suitable for detecting an insulation status between a high voltage power and a low voltage power of a vehicle. The insulation detection circuit includes a first energy storage unit, an impedance unit, a constant current unit, and a detection unit. The first energy storage unit is coupled to the high voltage power. The impedance unit is coupled between the first energy storage unit and a low voltage power. The constant current unit is coupled between the first energy storage unit and the impedance unit, and provides a constant current to pass through the impedance unit. The detection unit is coupled to the impedance unit, for detecting a current change of the current flowing through the impedance unit. When the detection unit detects that the current flowing through the impedance unit is smaller than a predetermined value, the detection unit then outputs a detection signal representing that the insulation status is abnormal.

On the basis of the above, the insulation detection circuit of this disclosure uses the constant current unit for providing a stable constant current to the second energy storage unit. When the current flowing through the second energy storage unit is smaller than a predetermined value, the detection unit may precisely detect that the insulation between the high voltage power and the low voltage power of the vehicle is damaged. Therefore, the present disclosure is able to enhance the usage convenience of the insulation detection circuits.

For further understanding of the present disclosure, reference is made to the following detailed description illustrating the embodiments and examples of the present disclosure. The description is only for illustrating the present disclosure and not for limiting the scope of the claim.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In a first embodiment,FIG. 1shows a function block diagram of an insulation detection circuit according to an embodiment of the disclosure. Please refer toFIG. 1. An insulation detection circuit1is suitable for detecting an insulation status between a high voltage power9and a low voltage power8of a vehicle. The insulation detection circuit1is coupled between a vehicle and a direct-current (DC) power, and the DC power is used for providing electric power to the vehicle, or for activating a power generator of the vehicle to provide electric power for the vehicle, so as to relatively form the high voltage power9and the low voltage power8. The insulation detection circuit1includes a first energy storage unit10, a second energy storage unit12, a constant current unit14, and a detection unit16.

Practically, the DC power can be implemented by a rechargeable battery, and the low voltage power8can be implemented by grounding the shell of the vehicle or using an electric instrument connection. There is a high impedance or insulation material between the high voltage power9and the low voltage power8for isolating the two voltage powers, thus the power will not leak from the high voltage power9to the low voltage power8. For example, the electric cable of a head lamp of the vehicle may be covered by an insulation rubber. When the insulation rubber is aging or damaged and thus makes the copper wire of the electric cable in the head lamp of the vehicle be in connection with the shell of the vehicle, electric power will leak from the high voltage power9to the low voltage power8. Therefore, the insulation detection circuit1in this disclosure is used for detecting the insulation status between the high voltage power9and the low voltage power8of the vehicle.

In addition, the high voltage power9is, for example, implemented by several serially connected rechargeable batteries. The rechargeable battery includes, for example, a lead-acid battery, a nickel-zinc battery, a nickel-iron battery, or a lithium battery, etc., and is not limited thereto. Practically, several rechargeable batteries are connected in series or in series-parallel for providing DC power to the electric instruments of the vehicle. Of course, the rechargeable battery can retain its electric quantity by means of power generators of the vehicle or voltage converters. Alternatively, the rechargeable battery can provide pulse DC power so as to be used by the electric instruments of the vehicle. The implementation types of the rechargeable battery are not limited in this embodiment.

The first energy storage unit10is coupled between the high voltage power9, the second energy storage unit12, the constant current unit14, and the detection unit16. The first energy storage unit10is able to isolate the high voltage power9from the low voltage power8, and can be implemented by a capacitor. Generally speaking, the capacitor can block the DC power from flowing from the high voltage power9to the low voltage power8, thus the capacitor has better isolation property than a resistor.

The second energy storage unit12is coupled between the first energy storage unit10and the low voltage power8, and can also be implemented by a capacitor. Generally speaking, the second energy storage unit12can store electric power under the condition of low frequency alternating-current (AC) current. Thus, when the insulation between the high voltage power9and the low voltage power8is damaged, the current leaking from the high voltage power9to the low voltage power8will conduct, so that the first energy storage unit10and the second energy storage unit12form a loop. Therefore, the first energy storage unit10provides a current division path for the constant current unit14, and the leakage current and the divided constant current will flow to the loop.

The constant current unit14is coupled to the first energy storage unit10, the second energy storage unit12, and the detection unit16. The constant current unit14is used for providing a stable and low frequency constant current to the second energy storage unit12, so as to charge/discharge the second energy storage unit12. When the current of the second energy storage unit12is smaller than a predetermined value, the detection unit16detects that the insulation between the high voltage power9and the low voltage power8is damaged. Practically, the constant current unit14can be implemented by a constant current circuit, a current mirror, a constant current diode, a switching power supply, which includes respectively several amplifiers and resistors, or by other coupling circuits including some electric components. Of course, the constant current unit14generates a constant current of low frequency AC for charging/discharging the second energy storage unit12. Thus, the second energy storage unit12can receive the constant current so as to be charged/discharged.

For example, the impedances of the first and the second energy storage units10and12are changed according to the frequency of the AC power provided by the constant current unit14. When the frequency of the AC power increases, the impedances of the first and the second energy storage units10and12will reduce. On the other hand, when the frequency of the AC power decreases, the first and the second energy storage units10and12will increase. Thus, in the present disclosure an AC power of a constant low frequency is used for charging/discharging the second energy storage unit12which is coupled to the low voltage power8. Thus the second energy storage unit12can have a constant impedance and an efficacy of not being influenced by the low voltage power8. Therefore, in the present disclosure the current change of the second energy storage unit12can be easily and precisely detected.

When the constant current unit14provides the AC power of a constant low frequency to the second energy storage unit12for charging/discharging, the impedance of the second energy storage unit12may be kept at a same constant value, and the impedance value of the second energy storage unit12will not be influenced no matter whether the insulation between the high voltage power9and the low voltage power8is damaged or not. Thus, the insulation detection circuit1may determine the insulation status between the two powers by detecting the current status of the second energy storage unit12.

Specifically, the constant current unit14provides a low frequency constant current for charging the second energy storage unit12, so that the second energy storage unit12receives the constant current normally. When the insulation status is abnormal, the first energy storage unit10will provide a current division path for the constant current unit14, so that the low frequency constant current provided by the constant current unit14may be divided to flow into the first energy storage unit10, thus the constant current received by the second energy storage unit12may be much smaller than the constant current received at the normal status. So, the detection unit16can easily and precisely detect the current change of the second energy storage unit12.

It's worth noting that one of the terminals of the first energy storage unit10is connected in floating to the high voltage power9and electrically interfered by the high voltage power9, thus the insulation detection precision of a common insulation detection circuit may be influenced. However, in the present disclosure, the constant current unit14provides a constant current to the second energy storage unit12, and the second energy storage unit12is made to be coupled between the first energy storage unit10and the low voltage power8, thus the electrical interference of the second energy storage unit12caused by the high voltage power9is reduced. Therefore, the insulation detection circuit1in this disclosure can increase the precision of the insulation detection.

In this embodiment, the detection unit16is coupled to the first energy storage unit10, the second energy storage unit12, and the constant current unit14. The detection unit16is used for detecting the current status of the second energy storage unit12. When the insulation between the high voltage power9and the low voltage power8is damaged and a leakage current is generated, the constant current unit14still maintains a stable constant current so as to charge/discharge the second energy storage unit12, and the first energy storage unit10and the second energy storage unit12form a loop. Therefore, the second energy storage unit12performs charging/discharging in the loop, so that the current status of the second energy storage unit12is changed according to the leakage current.

In addition, the detection unit16can also detect the voltage status of the second energy storage unit12. Practically, the voltage level of the second energy storage unit12changes according to the constant current, and the detection unit16is used for detecting the voltage level changes of the second energy storage unit12. Of course, the detection unit16can also detect the highest voltage level, the lowest voltage level, the highest voltage level and the lowest voltage level, or can output a detection signal which represents that the insulation status is abnormal when the voltage amplitude is smaller than the predetermined value. The one skilled in the art knows the function of detecting the voltage status, thus the function will not be redundantly described herein.

For example, the current of the second energy storage unit12is discharged or divided to the first energy storage unit10, thus the current of the second energy storage unit12is smaller than the predetermined value. For example, when the current of the second energy storage unit is smaller than 0.1 A, the detection unit16detects that the insulation between the high voltage power9and the low voltage power8is damaged. Of course, the predetermined value of the current of the second energy storage unit12can be modified by those skilled in the art according to actual design requirements.

For example, when the insulation status between the high voltage power9and the low voltage power8is good, the current flowing through the second energy storage unit12is relatively larger, thus the detection unit16detects that the current flowing through the second energy storage unit12is larger than the predetermined value. Therefore, the present disclosure can determine that no leakage current is generated between the high voltage power9and the low voltage power8.

When the insulation status between the high voltage power9and the low voltage power8is damaged, the current flowing through the second energy storage unit12is relatively lower, thus the detection unit16detects that the current flowing through the second energy storage unit12is smaller than the predetermined value. Therefore, the detection unit16outputs a detection signal which represents that the insulation status is abnormal, so as to determine whether the leakage current is generated between the high voltage power9and the low voltage power8. Therefore, the present disclosure uses the detection circuit formed by the constant current unit14and the detection unit16for determining whether the insulation status between the high voltage power9and the low voltage power8is good or not.

It's worth noting that, in other embodiments, the detection unit16can be coupled between the second energy storage unit12and the low voltage power8, so that the detection unit16can detect the voltage or current changes of the second energy storage unit12. The embodiments in this disclosure do not limit the implementation types of the detection unit16. In addition, the detection unit16may be coupled to the electric power control system of the vehicle. When the detection unit16detects the signals which represent that the insulation between the high voltage power9and the low voltage power8is damaged, the detection unit16can transmit the detection signals through the control area network (CAN), so as to let the display instruments or warning devices of the vehicle output the display or warning signals, in order to protect the users.

Therefore, in the present disclosure the constant current unit14generates a constant low-frequency pulse AC power, for charging the second energy storage unit12. When the insulation between the high voltage power9and the low voltage power8is damaged, the constant current provided by the constant current unit14may be divided to flow into the first energy storage unit10, and the second energy storage unit12may be charged or discharged in the loop, thus the current flowing through the second energy storage unit12will change, and the detection unit16can detect the insulation status between the high voltage power9and the low voltage power8.

In addition, the first and the second energy storage units10and12are capacitors which are able to isolate the high voltage power9from the low voltage power8, thus there are good insulations between the high voltage power9and the low voltage power8, and the risk of generating a trace amount of high voltage leakage current will be avoided. Moreover, the detection unit16detects the second energy storage unit12which is connected with the low voltage power8, so that the possibility that the second energy storage unit12is interfered by the high voltage power9is reduced, and the precision of insulation detection is enhanced.

In a second embodiment, the circuit structure of the constant current unit14inFIG. 1may be implemented by different circuits. Of course, the constant current14can still provide a stable constant current to the second energy storage unit12, so that the detection unit16can detect the insulation status between the high voltage power9and the low voltage power8.

FIG. 2Ashows a circuit structure diagram of an insulation detection circuit according toFIG. 1of an embodiment of the present disclosure. Please refer toFIG. 2A. For convenience of explanation, the first and the second energy storage units are respectively the first and the second capacitors100and120. The constant current unit14includes a first amplifier141, a second amplifier142, and a plurality of resistors144,145,146,148, and150. The constant current unit14is used for outputting a stable constant current to the second capacitor120. The coupling relations among the first amplifier141, the second amplifier142, and the resistors144,145,146,148, and150can be freely designed by the one skilled in the art according to the actual requirements.

The non-inverting input terminal of the first amplifier141shown inFIG. 2Ais grounded, the inverting input terminal of the first amplifier141is coupled to an input voltage Vin, and the output terminal of the first amplifier141is coupled between the inverting input terminal of the second amplifier142and the detection unit16. The non-inverting input terminal of the second amplifier142is coupled between the non-inverting input terminal of the first amplifier141and the output terminal of the second amplifier142, and the resistors144,145,146,148, and150are coupled to the first amplifier141or the second amplifier142.

For example, the resistor148is coupled to the non-inverting input terminal of the first amplifier141. Because the first amplifier141serves as a subtractor, if the input voltage Vin and the resistor144are fixed, a constant current will be generated. Of course, in other embodiments, the number and coupling manners of the resistors144,145,146,148, and150can be freely designed by the one skilled in the art according to actual requirement.

Specifically, when the insulation status between the high voltage power9and the low voltage power8is good, the equivalent switch18between the high voltage power9and the low voltage power8can be regarded as being turned off. For example, the low frequency pulse signal may be provided by the computer of the vehicle to the constant current unit14, and is processed into a low-frequency pulse constant current by means of the coupled circuit composed of the first amplifier141, the second amplifier142, and the resistors144,145,146,148, and150. Thus the constant current unit14may charge/discharge the coupling second capacitor120. Therefore, the constant current unit14charges/discharges the second capacitor120by means of a stable constant current generated by the first amplifier141, the second amplifier142, and the resistors144,145,146,148, and150.

When the insulation between the high voltage power9and the low voltage power8is damaged, the equivalent switch18between the high voltage power9and the low voltage power8may be regarded as conducting status. Thus the first and the second capacitors100and120and the equivalent switch18form a loop, and the first capacitor100can also receive part of the constant current generated by the constant current unit14, wherein the constant current is divided to flow into the loop, and the second capacitor120is discharged through the loop, thus the charge status of the second capacitor120and the current flowing through the second capacitor120are changed. Therefore, the detection unit16may be able to detect the voltage of the second capacitor120or the current flowing through the second capacitor120, so as to further determine the insulation status between the high voltage power9and the low voltage power8.

Please refer toFIG. 2Aagain, the first capacitor100can isolate the high voltage power9from the low voltage power8. However, one terminal of the first capacitor100is coupled to the electric appliance of the high voltage power9, thus the first capacitor100may be influenced by the electrical interference of the high voltage power9. On the other hand, the present disclosure detects the current or voltage changes of the second capacitor120. The second capacitor120is not influenced by the high voltage power9, and the high voltage power9is effectively isolated by means of the first capacitor100, thus the precision of the insulation detection circuit1is enhanced.

Therefore, in the present disclosure a constant low-frequency pulse AC power is generated by means of the constant current unit14, so as to charge/discharge the coupling second capacitor120. When the insulation between the high voltage power9and the low voltage power8is damaged, the constant current provided by the constant current unit14may be divided to flow into the first capacitor100, and the constant current flowing through the coupling second capacitor120may be changed. Thus, by detecting whether the current flowing through the second capacitor120is lower than a predetermined value or not, the detection unit16can detect the insulation status between the high voltage power9and the low voltage power8.

In addition, the coupling first capacitor100can isolate the high voltage power9from the low voltage power8, thus the insulation between the high voltage power9and the low voltage power8is good, and the risk of generating a trace amount of high voltage leakage current will be avoided. Moreover, the constant current unit14provides a low frequency constant current to the coupling second capacitor120, thus lets the coupling second capacitor120receive the constant current in the status of isolating the electrical interference of the high voltage power9, therefore, the possibility that the coupling second capacitor120is interfered by the high voltage power9is reduced. Of course, the detection unit16detects the current of the second capacitor120under the status of isolating the electrical interference of the high voltage power9, so as to increase the precision of the insulation detection circuit1.

In this embodiment, when the insulation between the high voltage power9and the low voltage power8is damaged, the constant current provided by the constant current unit14may be divided to flow into the first capacitor100, and the coupling second capacitor120is charged or discharged in the loop. The current division of the constant current makes the highest voltage level and the lowest voltage level of the second capacitor120change, thus the detection unit16may be able to detect the insulation status between the high voltage power9and the low voltage power8by detecting whether the highest voltage level, the lowest voltage level, the highest voltage level and the lowest voltage level, or the voltage amplitude is smaller than a predetermined value or not.

In the third embodiment,FIG. 2Bis a voltage waveform diagram of the insulation detection circuit of another embodiment of the present disclosure according toFIG. 2A. Please refer toFIG. 2B.FIG. 2Bshows the voltage waveform of the second capacitor120in a normal status and an abnormal status. When the insulation status between the high voltage power9and the low voltage power8is normal, the detection unit16detects that the voltage waveform of the second capacitor120is shown as that in the time period N ofFIG. 2B. When the insulation status between the high voltage power9and the low voltage power8is abnormal, the detection unit16detects that the voltage waveform of the second capacitor120is shown as that in the time period D ofFIG. 2B.

To describe in detail, generally the waveforms of the voltage or current detected by the insulation detection circuit are the ripple waves which have unobvious voltage drop or current difference, thus it's hard for a general insulation detection circuit to precisely detect the voltage or current changes. The present disclosure provides a low-frequency constant current by means of the constant current unit14for charging/discharging the second capacitor120. When the insulation status between the high voltage power9and the low voltage power8is abnormal, the first and the second capacitors100and120form a loop, and the constant current provided by the constant current unit14is divided to flow into the first capacitor100of the loop. At this moment, not all of the constant current is flowing into the second capacitor120, thus the voltage waveform of the second capacitor120may generate a relatively larger voltage drop, such as the voltage waveform shown in the time period D of theFIG. 2B. For example, if the 480 k ohms insulation from the high voltage power9side to the low voltage power8side is damaged, the detection unit16can detect that the voltage Va is 36.8 mV while the voltage Vb is 73.6 mV. Therefore, the detection unit16of the insulation detection circuit1can easily and precisely detect the abnormal insulation condition.

In the fourth embodiment, the insulation detection circuit1can be implemented by different manners.FIG. 3shows a circuit structure diagram of an insulation detection circuit according to another embodiment of the present disclosure. Please refer toFIG. 3. The structure of the insulation detection circuit2inFIG. 3is similar to the structure of the insulation detection circuit1in FIG.2A, and in the following descriptions the same symbols are used for representing the same components in both the insulation detection circuits1and2. The difference between the insulation detection circuits1and2consists in that the insulation detection circuit2further has a constant current compensation unit17. The constant current compensation unit17includes a third amplifier171, a fourth amplifier172, and a plurality of resistors174,175,176,177, and178. The present embodiment does not limit the implementation types of the constant current compensation unit17.

Specifically, the inverting input terminal of the third amplifier171is coupled to a first input voltage V1, and the non-inverting input terminal of the third amplifier171is coupled to a second input voltage V2, such as the first and the second input voltage V1and V2provided by the computer of the vehicle. The output terminal of the third amplifier171is coupled between the inverting input terminal of the fourth amplifier172, the constant current unit14, and the detection unit16. The non-inverting input terminal of the fourth amplifier172is coupled between the non-inverting input terminal of the third amplifier171and the output terminal of the fourth amplifier172. The resistors174,175,176,177, and178are coupled to the third amplifier171or the fourth amplifier172, as shown inFIG. 3. Thus, the constant current compensation unit17can compensate the losses in circuit of the constant current unit14.

For example, the constant current unit14outputs the constant current to the second capacitor120. The path from the constant current unit14to the second capacitor120has an impedance151, and the impedance151may cause the losses of current. The constant current compensation unit17is used for compensating the losses of the current. Therefore, the insulation detection circuit2may be able to detect the current value of the second capacitor120more precisely.

In the fifth embodiment,FIG. 4is a circuit structure diagram of an insulation detection circuit according to another embodiment of the present disclosure. Please refer toFIG. 4. The insulation detection circuit3is similar to the insulation detection circuit1in the second embodiment. For example, the insulation detection circuit3can also provide constant current to the second capacitor120, thus the detection unit16may be able to detect the changes of the current value of the second capacitor120. However, there still exists difference between the insulation detection circuits1and3, and the difference consists in that the constant current unit14ais implemented through the circuit structure of a current mirror.

Specifically, the constant current unit14aincludes a current source140a, a first transistor142a, and a second transistor144a. The first and the second transistors142aand144aare, for example, the power transistors, the field-effect transistors, or the bipolar junction transistors, and the present embodiment does not limit the implementation types of the first and the second transistors142aand144a. Practically, the current source140ais coupled to the collector node of the first transistor142a, and the base node of the first transistor142ais coupled to the base node of the second transistor144a. Moreover, the wire is coupled between the base nodes of the first and the second transistors142aand144aand coupled to the collector node of the first transistor142a, so as to generate a mirror reflection current. The present embodiment does not limit the implementation types of the current mirror.

In the sixth embodiment,FIG. 5shows a structure diagram of an insulation detection circuit according to another embodiment of the present disclosure. Please refer toFIG. 5, the insulation detection circuit4in this embodiment is similar to the insulation detection unit1in the above embodiment. For example, the insulation detection circuit4can also provide a constant current to the second capacitor120, thus the detection unit16may be able to detect the changes of the current of the second capacitor120. However, there still exists difference between the insulation detection circuits1and4, and such difference consists in that the constant current unit14bcan be implemented by a constant current diode140b.

The constant current unit14bincludes a current input terminal141b, a current output terminal142b, a constant current diode140b, and a resistor143b, and the resistor143band the constant current diode140bare connected in parallel, as shown inFIG. 5. The current input terminal141bis electrically connected with the input voltage Vin, such as the input voltage Vin provided by the computer of the vehicle. The anode of the constant current diode140bis electrically connected with current input terminal141b, and the cathode of the constant current diode140bis electrically connected with the current output terminal142b. The resistor143bis connected in parallel with the constant current diode140b. In other embodiments, the resistor143bcan be replaced by an inductor or a capacitor, for adjusting the current outputted by the constant current unit14b. The present embodiment does not limit the implementation types of the constant current unit14b.

For example, when the input voltage Vin generates a half period waveform, the current will be transmitted from the current input terminal141bto the constant current diode140b, and then will be outputted to the second capacitor120through the current output terminal142b. The properties of the constant current diode140binclude that if it receives a forward voltage, it will output a rated value of current, no matter how much the voltage is. Therefore, identical current is acquired so long as the value of the voltage lies within the standard of the constant current diode140b. Thus, after adding the constant current diode140b, even if the AC voltage generates 10% voltage change, the current will not change due to the voltage change, and the efficacy of outputting a stable constant current is achieved.

In the seventh embodiment,FIG. 6shows a flow chart of an insulation detection method according to another embodiment of the present disclosure. Please refer toFIG. 6, an insulation detection method is disclosed. The method is suitable for detecting an insulation status between a high voltage power and a low voltage power of a vehicle. The insulation detection method include: at first, in the step S601, providing a first energy storage unit coupled to the high voltage power, and providing a second energy storage unit coupled between the first energy storage unit and the low voltage power.

Then in step S603, the method includes providing a constant current for charging/discharging the second energy storage unit. In step S605, the method includes detecting the current changes of the current flowing through the second energy storage unit. In step S607, the method includes determining whether the current flowing through the second energy storage unit is smaller than a predetermined value or not. If the current flowing through the second energy storage unit is smaller than the predetermined value, the step S609is then executed, and the detection unit outputs a detection signal representing that the insulation status is abnormal. If the current is not smaller than the predetermined value, the method then goes back to the step S605, and the detection unit continuously detects the current changes of the current flowing through the second energy storage unit.

It's worth noting that, the step S605further includes that the voltage level of the second energy storage unit changes according to the constant current, thus the detection unit can also detect the voltage level changes of the second energy storage unit. Therefore, the step S607may further include determining whether the highest voltage level, the lowest voltage level, the highest and the lowest voltage levels, or the voltage amplitude is smaller than a predetermined value or not. If so, the step S609is then executed, and the detection signal representing that the insulation status is abnormal is outputted. If not, the step S605is then executed. The present embodiment does not limit the implementation types of the insulation detection method.

In the eighth embodiment,FIG. 7Ashows a function block diagram of an insulation detection circuit according to another embodiment of the present disclosure.FIG. 7Bis a structural diagram of the insulation detection circuit of another embodiment of the present disclosure according toFIG. 7A. Please refer toFIGS. 7A and 7B. The insulation detection circuit5in this embodiment is similar to the insulation detection circuit1in the above embodiment, for example, the insulation detection circuit5can also provide the constant current to the impedance unit13, thus the detection unit16can be able to detect the current changes of the impedance unit13. However, there still exists difference between the insulation detection circuits1and5, and the difference consists in that the insulation detection circuit5uses an impedance unit13for replacing the second energy storage unit, and the impedance unit13is coupled between the first energy storage unit10and the low voltage power8.

Practically, the impedance unit13is used for attenuating the voltage. When the insulation between the high voltage power9and the low voltage power8is damaged, the impedance unit13may cause a voltage drop between the high voltage power9and the low voltage power8, thus the detection unit16may be able to detect the current changes of the impedance unit13.

Specifically, the constant current unit14provides a constant current to pass through the impedance unit13. The detection unit16detects the current changes of the current flowing through the impedance unit13. When the detection unit16detects that the current flowing through the impedance unit13is smaller than a predetermined value, then a detection signal representing that the insulation status is abnormal is outputted.

Please refer toFIGS. 7A and 7Bagain, the first energy storage unit10is a first capacitor100, and the impedance unit13is a resistor130. The resistor130is coupled between the first capacitor100and the low voltage power8. When the insulation between the high voltage power9and the low voltage power8is damaged, the constant current will be divided to flow into the first capacitor100, and the first capacitor100and the resistor130form an RC loop, so that the current flowing through the resistor130is smaller than the predetermined value.

On the basis of the above, the present disclosure provides an insulation detection circuit, which provides a stable constant current to the second energy storage unit for charging/discharging it. When the constant current is divided to flow into the first energy storage unit, the current flowing through the second energy storage unit will be smaller than a predetermined value, thus the detection unit can be able to precisely detect that the insulation between the high voltage power and the low voltage power of the vehicle is damaged. Therefore, the present disclosure is able to increase the usage convenience of the insulation detection circuit, and can achieve the aforementioned objects.

Some modifications of these examples, as well as other possibilities will, on reading or having read this description, or having comprehended these examples, occur to those skilled in the art. Such modifications and variations are comprehended within this disclosure as described here and claimed below. The description above illustrates only a relative few specific embodiments and examples of the present disclosure. The present disclosure, indeed, does include various modifications and variations made to the structures and operations described herein, which still fall within the scope of the present disclosure as defined in the following claims.