Test circuit and test method for chargeable electronic product circuit board

Abstract

A test circuit and test method for a circuit board of a rechargeable electronic product includes a circuit board under test, a rechargeable battery, a charging detection module, and a microprocessor. It also includes an analog power adapter that can provide power for charging tests under normal supply voltage conditions and power for over-limit charging tests where the supply voltage exceeds the normal supply voltage. Furthermore, it includes a charging completion detection module that stops charging when a preset full charge condition is reached under the control of the microprocessor, and a switch control module that sequentially performs normal charging tests, over-limit charging tests, and charging completion tests at the same test station under the control of the microprocessor.

Description

Technical Field

[0001] This invention pertains to testing technologies for electronic products, and particularly relates to testing technologies for electronic products equipped with rechargeable batteries. Background Technology

[0002] As the manufacturing barriers for consumer electronics products—such as electric hair clippers, electric shavers, hair dryers, electric breast pumps, LED lights, electric toothbrushes, and battery-powered power tools—gradually decrease, especially for handheld and portable consumer electronics, these products are characterized by large-scale production and short production cycles. For the testing of PCBAs of these consumer electronics products, a functional-based testing approach is commonly used, generally including button function testing, display or indicator function testing, load drive function testing, adapter overcharge protection testing, normal charging function testing, and quiescent current testing. A key commonality among these products is the inclusion of rechargeable batteries, such as nickel-metal hydride or lithium-ion batteries. Therefore, after the circuit board assembly of these products is completed, conducting charging-related electrical performance tests is a necessary and important test item. The most common tests include:

[0003] 1. Charging voltage over-limit test—When the circuit board under test is subjected to a preset charging voltage that exceeds the normal charging voltage, can the charging protection module inside the circuit board under test disconnect the abnormal voltage charging in time to avoid damaging the circuit board under test?

[0004] 2. Charging current test—The circuit board under test is charged under normal charging voltage. The charging current value and battery voltage value are checked to see if they are within the normal range, so as to determine whether the charging function of the circuit board under test is normal.

[0005] 3. Charging Completion Test — This test verifies whether the circuit board under test can automatically stop charging when it reaches the preset full charge condition, in order to avoid overcharging and damage to the battery or circuit.

[0006] For the aforementioned tests, existing technologies typically employ a single-item testing approach, meaning one test station is configured for each test item. Three test items require three sets of testing equipment and three test stations. The disadvantages are: because there are three independent test stations, three processes are needed to complete the three test items, resulting in an excessive number of test stations, testing processes, and three sets of testing equipment. This is neither conducive to saving production costs nor improving production efficiency.

[0007] Therefore, integrating the above three electrical performance test items into a continuous automated test can not only save test equipment and manpower, but also greatly shorten the test cycle and achieve higher test efficiency. Summary of the Invention

[0008] To address the aforementioned technical problems, this invention provides a test circuit and test method for circuit boards of rechargeable electronic products, enabling the continuous, step-by-step completion of the three test items at a single test station. The technical solution of this invention is as follows:

[0009] A test circuit for a circuit board of a rechargeable electronic product includes a circuit board under test, a rechargeable battery, a charging detection module, and a microprocessor. It also includes an analog power adapter that can provide power for charging tests under normal supply voltage conditions and power for over-limit charging tests where the supply voltage exceeds the normal supply voltage. Furthermore, it includes a charging completion detection module that, under the control of the microprocessor, terminates charging when a preset full charge condition is reached. Finally, it includes a switch control module that, under the control of the microprocessor, sequentially performs normal charging tests, over-limit charging tests, and charging completion tests at the same test station for a single test.

[0010] Furthermore, the analog power adapter includes a first power supply for supplying a +5V power voltage to the test circuit and the circuit board under test, and a second power supply for supplying a +6V power voltage required for over-limit charging testing to the circuit board under test.

[0011] Preferably, the switch control module includes: a first switch unit that connects or disconnects the first power supply to the circuit board under test, a second switch unit that connects or disconnects the second power supply to the circuit board under test, a fourth switch unit that connects or disconnects the charging detection module to the circuit board under test, a fifth switch unit that connects or disconnects the charging completion detection module to the first power supply, and a third switch unit that switches between the rechargeable battery and the charging completion detection module.

[0012] Preferably, the first switching unit includes a first relay, and also includes a first field-effect transistor whose drain is connected to one end of the first relay coil and whose source is grounded. The other end of the first relay coil is connected to a first power supply. The gate of the first field-effect transistor is connected to one end of a first resistor and one end of a second resistor. The other end of the second resistor is connected to a first output interface of the microprocessor. The other end of the first resistor is grounded. The first relay includes a first normally open contact disposed between the first power supply and the first interface of the circuit board under test.

[0013] The second switching unit includes a second relay, and a second field-effect transistor whose drain is connected to one end of the second relay coil and whose source is grounded. The other end of the second relay coil is connected to a first power supply. The gate of the second field-effect transistor is connected to one end of a third resistor and one end of a fourth resistor. The other end of the fourth resistor is connected to the second output interface of the microprocessor. The other end of the third resistor is grounded. The second relay includes a second normally open contact disposed between the second power supply and the first interface of the circuit board under test.

[0014] The third switching unit includes a third relay and a third field-effect transistor whose drain is connected to one end of the third relay coil and whose source is grounded. The other end of the third relay coil is connected to a first power supply. The gate of the third field-effect transistor is connected to one end of a tenth resistor and one end of an eleventh resistor. The other end of the tenth resistor is connected to the third output interface of the microprocessor, and the other end of the eleventh resistor is grounded. The third relay includes a normally closed contact between the positive terminal of the rechargeable battery and the third interface of the circuit board under test, and a normally open contact between the third interface of the circuit board under test and the charging completion detection module. The negative terminal of the rechargeable battery is connected to the second interface of the circuit board under test.

[0015] Preferably, the fourth switching unit includes a fourth field-effect transistor whose drain is connected to the fourth interface of the circuit board under test, whose source is connected to the first sampling resistor, and whose other end is grounded. It also includes a sixth resistor and a fifth resistor connected to the gate of the fourth field-effect transistor, the other end of the sixth resistor being connected to the fourth output interface of the microprocessor, and the other end of the fifth resistor being grounded.

[0016] Preferably, the fifth switching unit includes a transistor and a fifth field-effect transistor, and further includes: a seventh resistor with one end connected to the first power supply and the source of the fifth field-effect transistor and the other end connected to the collector of the transistor; an eighth resistor with one end connected to the gate of the fifth field-effect transistor and the other end connected to the collector of the transistor; and a ninth resistor with one end connected to the base of the transistor and the other end connected to the fifth output interface of the microprocessor, wherein the emitter of the transistor is grounded.

[0017] Preferably, the charging detection module includes a current detection module, which includes a sampling resistor with one end connected to the source of the fourth field-effect transistor and the other end grounded. The source of the fourth field-effect transistor is connected to the first input interface of the microprocessor. The module also includes a rechargeable battery voltage detection module, which includes a sampling voltage divider resistor, a twelfth resistor and a thirteenth resistor, connected to the second input interface of the microprocessor. One end of the twelfth resistor is connected to the positive terminal detection contact (BATTER+) of the rechargeable battery, and the other end of the thirteenth resistor is grounded.

[0018] Preferably, the charging completion detection module includes a fifth field-effect transistor, a fourth diode, a first Zener diode, a first capacitor, and a fiftieth resistor. The positive terminal of the fourth diode is connected to the drain of the fifth field-effect transistor, and the negative terminal of the fourth diode is connected to the negative terminal of the first Zener diode, the positive terminal of the first capacitor, one end of the tenth resistor, and the normally open contact of the third relay. The positive terminal of the first Zener diode, the negative terminal of the first capacitor, and the other end of the fiftieth resistor are grounded.

[0019] In the above technical solution, the microprocessor is an STM8S103 microcontroller, and the first, second, third, fourth and fifth field-effect transistors are enhancement-channel MOSFETs.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] This invention provides a solid technical foundation for completing all functional tests of a PCBA (Printed Circuit Board Assembly) on a single testing device. When combined with technical solutions for other test items related to this invention, all test items can be completed using a single testing device and one person, not only shortening testing time but also reducing testing equipment and labor costs. The table below compares the practical application data of this invention with existing technologies:

[0022]

[0023] Attached image description:

[0024] Figure 1 This is a schematic diagram of the system modules according to an embodiment of the present invention;

[0025] Figure 2 This is a schematic diagram of the MCU pinout according to an embodiment of the present invention;

[0026] Figure 3 This is a schematic diagram of an analog adapter circuit according to an embodiment of the present invention;

[0027] Figure 4 This is a schematic diagram of the test circuit according to an embodiment of the present invention;

[0028] Figure 5 This is a schematic diagram of the test process according to an embodiment of the present invention. The present invention uses three test items—overvoltage charging inspection test, charging inspection test, and charging completion inspection test—as examples, and describes the technical solution of the present invention in detail with reference to the accompanying drawings.

[0029] Figure 1 The system modules shown in this embodiment of the invention include a circuit board under test (TBD), a rechargeable battery for testing, a charging detection module, a microprocessor U3, an analog power adapter, and a switch control module. These modules constitute a test circuit disposed in a testing device. The TBD and the testing device are electrically connected via probes on a test bed and test points located on the TBD. These test points include interface 1, interface 2, interface 3, and interface 4 of the TBD, as well as other test solder joints (such as...). Figure 2 The test point BATTER+ and Figure 4The test point is the positive terminal of the rechargeable battery (BATTER + test point). The rechargeable battery BATTER is the same as the battery supplied with the product under test, to provide a realistic working scenario of the circuit board under test being powered and charged by the product's battery. When the product under test is different, the battery supplied will also be different, and the corresponding test battery needs to be connected. In this embodiment, a lithium battery is used, but this invention is also applicable to rechargeable battery products such as nickel-metal hydride batteries. Considering cost and ease of maintenance, under the conditions of meeting performance requirements and ensuring quality, the microprocessor U3 used in this embodiment is a single-chip microcomputer of model STM8S103, which is a commercially available, inexpensive MCU with relatively rich input / output interfaces and relatively complete functions. For the same reason, the field-effect transistors (Q1, Q2, Q3, Q4, and Q5) in this embodiment use commercially available enhancement-channel MOSFETs of the same model, and the first, second, and third relays in this embodiment also use commercially available small solid-state relays of the same model.

[0030] Figure 2 The diagram shows some of the MCU's external interfaces and their markings, including a first output interface o_5V, a second output interface o_6V, a third output interface o_batt_anode, and a fourth output interface o_power-. All four output interfaces output level switching signals for real-time control of the switching module. It also includes a first input interface ad_charge and a second input interface adc_batt, both of which receive ADC signals to measure the sampled values ​​of the charging current and battery voltage, respectively.

[0031] Figure 3 The circuit configuration of the analog power adapter is shown. An external DC power supply is connected through three ports: 12V, 5V, and GND. The external 5V power supply, after passing through a filter capacitor C7, serves as the first power supply (+5V) for the analog power adapter and also provides a power signal indication for the test device, including a resistor R14 and an LED. The external 12V power supply is connected to the input terminal of a three-terminal voltage regulator chip U1 via a parallel filter capacitor C4. The adjustment terminal of the three-terminal voltage regulator chip U1 is connected to a standard resistor R16, and a resistor R15 is connected across its output terminal and the adjustment terminal. After filtering by parallel capacitors C5 and C6, the output terminal of the three-terminal voltage regulator chip U1 serves as the second power supply (+6V) for the analog adapter. It should be noted that the voltage of commercially available standard power adapters is 5±5%V, i.e., 4.75 to 5.25V. For some products, the over-limit voltage of the adapter used during testing should be based on the actual voltage requirement of the product, which may be 5.5V or 5.8V, etc.

[0032] Figure 4 The test circuit of the present invention is shown. Figure 4The switching control module includes a first switching unit and a second switching unit, used to switch between over-limit charging tests and normal charging tests, respectively. The first relay K1 and the second relay K2 each have a normally open single contact. The contact of relay K1 is connected between the 5V output terminal of the analog power adapter and interface 1 of the circuit board under test; the contact of relay K2 is connected between the 6V output terminal of the analog power adapter and interface 1 of the circuit board under test. The coil of relay K1 is driven by the first field-effect transistor Q1, and the coil of relay K2 is driven by the second field-effect transistor Q2. Protection diodes D1 and D2 are connected in parallel across the two ends of the coils. Real-time control of the conduction and cutoff of the field-effect transistor Q1 is achieved through the first output interface o-5V of the microprocessor U1 connected to the gate of the field-effect transistor Q1. In practical applications, a first resistor R1 and a second resistor R2 are also connected between the field-effect transistor Q1 and the microprocessor U1. Similarly, the real-time control of the on and off states of the field-effect transistor Q2 is achieved through the second output interface o_6V of the microprocessor U1 connected to the gate of the field-effect transistor Q2, and also includes the third resistor R3 and the fourth resistor R4 connected between the field-effect transistor Q2 and the microprocessor U1.

[0033] The third relay K3 is a double relay with normally closed contacts 5 and 6. It is driven by the third field-effect transistor Q3. The protection diode D3 is connected in parallel across the coil of the relay switch K3. The drain of the field-effect transistor Q3 is connected to interface 3 of the circuit board under test, its source is grounded, and its gate is connected to one end of the tenth resistor R10 and one end of the eleventh resistor R11. The other end of resistor R10 is connected to the third output interface o_batt_anode of the microprocessor, and the other end of resistor R11 is grounded.

[0034] The switching module also includes a fourth switching unit and a fifth switching unit. These two switching units directly use field-effect transistors as switches. The fourth switching unit includes a fourth field-effect transistor Q4 whose drain is connected to the interface 4 of the circuit board under test and whose source is connected to the first sampling resistor TR1. It also includes a sixth resistor R6 and a fifth resistor R5 connected to the gate of the field-effect transistor Q4. The other end of resistor R6 is connected to the fourth output interface o_power- of the microprocessor, and the other end of resistor R5 is grounded.

[0035] The fifth switching unit includes a transistor Q6 and a fifth field-effect transistor Q5, and also includes: a seventh resistor R7 with one end connected to the first power supply +5V and the source of the fifth field-effect transistor Q5 and the other end connected to the collector of the transistor Q6; an eighth resistor R8 with one end connected to the gate of the field-effect transistor Q5 and the other end connected to the collector of the transistor Q6; and a ninth resistor R9 with one end connected to the base of the transistor Q6 and the other end connected to the fifth output interface o_charge_ok of the microprocessor. The emitter of the transistor Q6 is grounded.

[0036] from Figure 4 Combination Figure 2 As can be seen, the charging detection module includes a charging current detection module and a battery voltage detection module. The current detection module includes a sampling resistor TR1 connected between the source of the MOSFET Q4 and ground. One end of the sampling resistor TR1 is connected to the first input interface ad_charge of the microprocessor. When Q4 is turned on, the charging current flows out from interface 4 of the circuit board under test, passes through the sampling resistor TR1, and generates a voltage signal. The microprocessor interface adc_charge acquires this voltage signal and processes the data to obtain the charging current value. The battery voltage detection module includes a detection point BATTER+ located at the positive terminal of the rechargeable battery, and includes... Figure 2 The microprocessor's second input interface, adc_batt, is shown connected to the rechargeable battery positive terminal detection contact (BATTER+) and voltage divider resistors R12 and R13. During charging, the rechargeable battery positive terminal remains connected to the normally closed contact 5 of relay K3.

[0037] Figure 4 The circuit configuration of the charging completion detection module is also shown, including a fifth field-effect transistor Q5, a fourth diode D4, a first Zener diode ZD1, a first capacitor C1, and a fiftieth resistor R50. The anode of diode D4 is connected to the drain of field-effect transistor Q5, and the cathode of diode D4 is connected to the cathode of Zener diode ZD1, the anode of electrolytic capacitor C1, one end of resistor R50, and the normally open contact 6 of third relay K3; the anode of Zener diode ZD1, the cathode of capacitor C1, and the other end of resistor R50 are grounded.

[0038] The following combination Figure 5 and Figure 4 The test items of this invention embodiment are described below:

[0039] First, the charging voltage over-limit test is performed. The circuit board under test (PCB) is placed in the test station. The negative terminal of the rechargeable battery is connected to interface 2 of the PCB (the negative terminal of the battery on the PCB). The positive terminal of the rechargeable battery is connected to interface 3 of the PCB (the positive terminal of the battery on the PCB) through the normally closed contact 5 of relay K3. At this time, the PCB powers on and performs a self-test. The test device detects the signal triggered by the position switch after the PCB is placed in the test station. The microprocessor U3 controls the MOSFET Q4 to conduct, and interface 4 of the PCB (the negative terminal of the power supply on the PCB) is connected to ground through sampling resistor TR1. Next, the microprocessor U3 turns on MOSFET Q2, relay K2 is energized, and the second power supply +6V is connected to interface 1 of the PCB (the positive terminal of the power supply on the PCB). At this time, the charging management module inside the PCB detects that the charging voltage is over-limit and immediately cuts off the charging circuit, stopping the charging process. The charging test module of the testing device can determine whether there is charging current by reading the sampling signal of the sampling resistor TR1. When the sampling current is zero, it indicates that the voltage over-limit protection function of the circuit board under test is normal, and the microprocessor U3 will control the signal unit on the testing device to give a signal indication of whether the limit is exceeded. For circuit boards under test equipped with over-limit charging indicator lights, the corresponding indicator signal can also be observed.

[0040] If the overvoltage charging test passes, the system automatically switches to the normal charging test. This test primarily measures the charging current to determine if the charging management module of the circuit board under test can control the charging current within a preset range. Microprocessor U3 cuts off Q2, releases relay K2, disconnecting the second power supply +6V. Then, it turns on Q1, energizes relay K1, and connects the circuit board under test to the first power supply +5V. When the charging management module of the circuit board under test detects that the charging voltage is within the normal range, it starts charging. The microprocessor U3 of the testing device reads the sampling current on sampling resistor TR1 and the sampling voltage on the positive terminal of the rechargeable battery. According to the set program, it determines whether the charging current of the circuit board under test and the voltage of the battery being charged are within the product design range and provides corresponding indication signals through the signal unit on the testing device.

[0041] After the normal charging test is completed, the test program will automatically switch to the charging completion test. This test checks whether the charging management module of the circuit board under test can automatically stop charging after the battery is fully charged to prevent overcharging. Microprocessor U3 first turns on transistor Q6, which in turn drives Q5 to turn on. At this time, Zener diode ZD1 is energized, and a standard voltage is obtained at its terminal. This standard voltage value is set to be exactly the same as the voltage of the rechargeable battery after it is fully charged. Next, microprocessor U3 turns on MOSFET Q3, and relay K3 is energized, switching the normally closed contact 6 to the normally open contact 6. At this time, the battery positive terminal outputs the rechargeable battery voltage. When the circuit board under test detects that the battery voltage has reached the preset value, it immediately cuts off the internal charging circuit and stops charging. At this time, the microprocessor determines whether the charging management module of the circuit board under test has stopped charging by reading the sampling current on the sampling resistor TR1. For circuit boards under test with a charging completion indicator light, the corresponding charging completion indicator signal can also be observed.

[0042] It should be noted that if any test result is found to be abnormal in the above tests, the test of that circuit board will be terminated, and after manually marking or sorting it, the next circuit board will be tested from scratch.

[0043] For circuit boards under test equipped with different types of rechargeable batteries and different shapes and sizes, the present invention can be conveniently applied to carry out the above-mentioned tests simply by configuring a suitable test bed, replacing the appropriate Zener diode ZD1, and adjusting the corresponding preset parameters in the software program.

[0044] The following are the test steps for the three test items mentioned above:

[0045] 1) The circuit board under test is located in the test bed. When the test circuit receives the position switch signal, it starts the over-limit charging test.

[0046] 2) Connect the rechargeable battery to the circuit board under test and perform a power-on self-test;

[0047] 3) The fourth field-effect transistor Q4 is turned on, and the sampling resistor TR1 is connected;

[0048] 4) When the second field-effect transistor Q2 is turned on, the second relay K2 is energized, and the second power supply is connected to the circuit board under test;

[0049] 5) Receive the current signal on the sampling resistor TR1 and perform data processing;

[0050] 6) Determine if the sampling current is greater than zero. If yes, issue an over-limit test abnormality signal and exit the test; otherwise, continue with the following test steps.

[0051] 7) The second relay K2 is released, disconnecting the circuit board under test from the second power supply, thus ending the over-limit charging test;

[0052] 8) When the first field-effect transistor Q1 is turned on, the first relay K1 is energized, the first power supply is connected to the circuit board under test, and the normal charging test begins.

[0053] 9) Receive the rechargeable battery BATTER+ voltage signal and the current signal on the sampling resistor TR1 and perform data processing;

[0054] 10) Determine whether the battery voltage and sampling current are within the preset range. If not, issue a charging test abnormality signal and exit the test; if yes, end the normal charging test and continue with the following test steps.

[0055] 11) Transistor Q6 and fifth field-effect transistor Q5 are turned on, the first Zener diode ZD1 is energized, charging is complete and the test begins;

[0056] 12) When the third field-effect transistor Q3 is turned on, the normally open contact of the third relay K3 is closed, and the standard voltage of the Zener diode ZD1 is connected to the circuit board under test.

[0057] 13) Receive the current signal on the sampling resistor TR1 and perform data processing;

[0058] 14) Determine if the sampling current is greater than zero. If yes, issue an over-limit test abnormality signal and exit the test; otherwise, issue a charging completion signal and continue with the following steps:

[0059] 15) When the first field-effect transistor Q1 is turned off, the first relay K1 is released, disconnecting the circuit board under test from the first power supply.

[0060] 16) When the third field-effect transistor Q3 is turned off, the third relay K3 is released and reset, disconnecting the Zener diode ZD1 from the circuit board under test;

[0061] 17) When transistor Q6 is cut off, the fifth field-effect transistor Q5 is cut off, disconnecting the charging completion module from the first power supply;

[0062] 18) When the fourth field-effect transistor Q4 is turned off, disconnect the charging current detection module from the circuit board under test, and the test ends.

[0063] The implementation methods and principles described above do not constitute a limitation on the scope of protection of this technical solution. Any modifications, equivalent substitutions, and imitations made within the ideas and principles of the above implementation methods should be included within the scope of protection of this technical solution.

Claims

1. A test circuit for a circuit board of a rechargeable electronic product, comprising the circuit board under test, a rechargeable battery, a charging detection module, and a microprocessor, characterized in that: The system includes an analog power adapter that provides power for charging tests under normal supply voltage conditions and power for over-limit charging tests where the supply voltage exceeds the normal supply voltage; a charging completion detection module that stops charging when a preset full charge condition is reached under microprocessor control; and a switch control module that performs a single test at the same testing station, sequentially combining normal charging tests, over-limit charging tests, and charging completion tests under microprocessor control. The switch control module includes a first switch unit that connects or disconnects the first power supply to the circuit board under test and a second power supply unit that connects the second power supply to the circuit board under test. The system includes a second switching unit for connecting or disconnecting the circuit board, a fourth switching unit for connecting or disconnecting the charging detection module from the circuit board under test, a fifth switching unit for connecting or disconnecting the charging completion detection module from the first power supply, and a third switching unit for switching between the rechargeable battery and the charging completion detection module. The fourth switching unit includes a fourth field-effect transistor whose drain is connected to the fourth interface of the circuit board under test and whose source is connected to the first sampling resistor. The other end of the first sampling resistor is grounded. The system also includes a sixth resistor and a fifth resistor connected to the gate of the fourth field-effect transistor. The other end of the sixth resistor is connected to the fourth output interface of the microprocessor, and the other end of the fifth resistor is grounded.

2. The test circuit for a chargeable electronic product circuit board of claim 1, wherein: The analog power adapter includes a first power supply with a +5V supply voltage to the test circuit and the circuit board under test, and a second power supply with a +6V supply voltage required for over-limit charging testing of the circuit board under test.

3. The test circuit for a chargeable electronic product circuit board of claim 1, wherein: The first switching unit includes a first relay, and also includes a first field-effect transistor whose drain is connected to one end of the first relay coil and whose source is grounded. The other end of the first relay coil is connected to a first power supply. The gate of the first field-effect transistor is connected to one end of a first resistor and one end of a second resistor. The other end of the second resistor is connected to a first output interface of the microprocessor. The other end of the first resistor is grounded. The first relay includes a first normally open contact disposed between the first power supply and the first interface of the circuit board under test. The second switching unit includes a second relay, and a second field-effect transistor whose drain is connected to one end of the second relay coil and whose source is grounded. The other end of the second relay coil is connected to a first power supply. The gate of the second field-effect transistor is connected to one end of a third resistor and one end of a fourth resistor. The other end of the fourth resistor is connected to the second output interface of the microprocessor. The other end of the third resistor is grounded. The second relay includes a second normally open contact disposed between the second power supply and the first interface of the circuit board under test. The third switching unit includes a third relay and a third field-effect transistor whose drain is connected to one end of the third relay coil and whose source is grounded. The other end of the third relay coil is connected to a first power supply. The gate of the third field-effect transistor is connected to one end of a tenth resistor and one end of an eleventh resistor. The other end of the tenth resistor is connected to the third output interface of the microprocessor, and the other end of the eleventh resistor is grounded. The third relay includes a normally closed contact located between the positive terminal of the rechargeable battery and the third interface of the circuit board under test, and a normally open contact located between the third interface of the circuit board under test and the charging completion detection module. The negative terminal of the rechargeable battery is connected to the second interface of the circuit board under test.

4. The test circuit for a chargeable electronic product circuit board of claim 3 wherein: The fifth switching unit includes a transistor and a fifth field-effect transistor, and further includes: a seventh resistor with one end connected to the first power supply and the source of the fifth field-effect transistor and the other end connected to the collector of the transistor; an eighth resistor with one end connected to the gate of the fifth field-effect transistor and the other end connected to the collector of the transistor; and a ninth resistor with one end connected to the base of the transistor and the other end connected to the fifth output interface of the microprocessor. The emitter of the transistor is grounded.

5. The test circuit for a chargeable electronic product circuit board of claim 1, wherein: The charging detection module includes a current detection module, which includes a sampling resistor with one end connected to the source of the fourth field-effect transistor and the other end grounded. The source of the fourth field-effect transistor is connected to the first input interface of the microprocessor. It also includes a rechargeable battery voltage detection module, which includes a sampling voltage divider resistor, the twelfth resistor, and a thirteenth resistor connected to the second input interface of the microprocessor. One end of the twelfth resistor is connected to the positive terminal detection contact BATTER+ of the rechargeable battery, and the other end of the thirteenth resistor is grounded.

6. The test circuit for a chargeable electronic product circuit board of claim 1, wherein: The charging completion detection module includes a fifth field-effect transistor, a fourth diode, a first Zener diode, a first capacitor, and a fiftieth resistor. The positive terminal of the fourth diode is connected to the drain of the fifth field-effect transistor, and the negative terminal of the fourth diode is connected to the negative terminal of the first Zener diode, the positive terminal of the first capacitor, one end of the tenth resistor, and the normally open contact of the third relay. The positive terminal of the first Zener diode, the negative terminal of the first capacitor, and the other end of the fiftieth resistor are grounded.

7. The test circuit for a chargeable electronic product circuit board of claim 4 wherein: the test circuit further comprises a plurality of test points. The microprocessor is an STM8S103 microcontroller, and the first, second, third, fourth, and fifth field-effect transistors are enhanced-channel MOSFETs. The rechargeable battery is a lithium battery.

8. A test method for a circuit board of a rechargeable electronic product, employing any one of the test circuits in 1-7, comprising the following test steps: 1) The circuit board under test is located in the test bed. When the test circuit receives the position switch signal, it starts the over-limit charging test. 2) Connect the rechargeable battery to the circuit board under test and perform a power-on self-test; 3) The fourth field-effect transistor is turned on, and the sampling resistor is connected; 4) The second field-effect transistor is turned on, the second relay is energized, and the second power supply is connected to the circuit board under test; 5) Receive the current signal on the sampling resistor and process the data; 6) Determine if the sampling current is greater than zero. If yes, issue an over-limit test abnormality signal and exit the test; otherwise, continue with the following test steps. 7) The second relay is released, disconnecting the circuit board under test from the second power supply, thus ending the over-limit charging test; 8) The first field-effect transistor is turned on, the first relay is energized, the first power supply is connected to the circuit board under test, and the normal charging test begins. 9) Receive the rechargeable battery voltage signal and the current signal on the sampling resistor and perform data processing; 10) Determine whether the rechargeable battery voltage and sampling current are within the preset range. If not, issue a charging test abnormality signal and exit the test; if yes, end the normal charging test and continue with the following test steps. 11) The transistor and the fifth field-effect transistor are turned on, the first Zener diode is energized, the charging is complete and the test begins; 12) The third field-effect transistor is turned on, the normally open contact of the third relay is closed, and the nominal voltage of the Zener diode is connected to the circuit board under test. 13) Receive the current signal on the sampling resistor and perform data processing; 14) Determine if the sampled current is greater than zero. If yes, issue a charging completion test abnormality signal and exit the test; otherwise, issue a charging completion test normal signal and continue with the following steps: 15) The first field-effect transistor is turned off, the first relay is released, and the circuit board under test is disconnected from the first power supply; 16) The third field-effect transistor is turned off, the third relay is released and reset, and the connection between the Zener diode and the circuit board under test is disconnected. 17) The transistor is cut off, the fifth field-effect transistor is cut off, and the connection between the charging completion module and the first power supply is disconnected; 18) When the fourth MOSFET is turned off, disconnect the charging current detection module from the circuit board under test, and the test ends.

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