Driver for driving electromechanical device

Abstract

To provide a driver for driving an electromechanical device having a solenoid and a mechanical switch.SOLUTION: An electromechanical system 500 includes a driver 520 coupled to an electromechanical device 510, such as a contactor, the driver including an input port VBATx, a ground port CLx, first and second output ports CHx, COx connectable to the electromechanical device, and two power switches HS, LS. A controller 530 operates in a first mode to charge a solenoid 512 and close a mechanical switch 514, a second mode to maintain the mechanical switch closed, and a third mode to discharge the solenoid and open the mechanical switch. In the first and second modes, the low-side power switch is on, and the high-side power switch is controlled to switch between an on-state and an off-state by the controller. In the off-state, a path is formed to ground via a ground diode D1, the solenoid, and the low-side power switch.SELECTED DRAWING: Figure 5A

Description

[Technical field]

[0001] The present disclosure relates to a driver for driving an electromechanical device, and more particularly, to a driver for driving a high voltage contactor device. [Background technology]

[0002] Contactor devices have two contact surfaces that are opened and closed to switch an electrical circuit on and off. They are used in high voltage and high current load applications, such as controlling large motors (such as in automobiles). Typically, contactors are opened and closed using an actuator, such as a solenoid. This actuator includes a plunger that is attached to the first surface of the contactor via a spring. The plunger is disposed within a coil of conductive material.

[0003] The solenoid is coupled to a drive circuit, which passes current through the solenoid's coil, causing electromagnetic induction. The magnetic force on the plunger moves the contacts from an open position to a closed position. To reopen the contactor, the solenoid's coil must be de-energized, reducing the magnetic force on the plunger. This de-energization process must be fast for safety and equipment integrity reasons. If the de-energization is not fast enough, the contacts can be damaged and welded together, preventing them from interrupting high voltage and creating a hazardous condition.

[0004] Traditionally, in circuits using solenoids, the coil is discharged through a freewheel path in the circuit. This solution is preferred due to its simple design, but if the contactor is used at high voltages, the freewheel path is not preferred because current continues to flow through the coil of the solenoid, slowing down the de-energization process and potentially fusing the contactor. Another solution that has been frequently used is to implement the freewheel path with a voltage clamp circuit, which discharges the coil when a threshold voltage is reached. Such a solution is described in an article in Gigavac Applications Note AN-016 entitled "Driving Contactors with external PWM" (https: / / www.sensata.com / sites / default / files / a / Sensata-gigavac-driving-contactors-with-external-pwm-app-note.pdf) by David Dong, Texas Instruments' "high-voltage contactor This information is described in the technical document entitled "High Voltage Contactor Control" (https: / / www.ti.com / lit / ml / slyp693 / slyp693.pdf?ts=1678105349002&ref_url=https%253A%252F%252Fwww.google.com%252F) and in the datasheets for the iC-JE and iC-GE PWM Relay / Solenoid Drivers from iC-Haus (https: / / www.ichaus.de / upload / pdf / JE_datasheet_G3en.pdf; https: / / www.ichaus.de / upload / pdf / GE_datasheet_B1en.pdf).

[0005] Clamp circuits are typically implemented with low clamping voltages, making them unsuitable for high voltage contactors, and often require the use of multiple power devices, increasing the area of ​​the driver and manufacturing costs. Summary of the Invention [Problem to be solved by the invention]

[0006] It is an object of the present disclosure to address one or more of the above-mentioned shortcomings. [Means for solving the problem]

[0007] According to a first aspect of the present disclosure, a driver for driving an electromechanical device including a solenoid and a mechanical switch is provided. The driver includes an input port connectable to a battery, a ground port connected to ground, and a first output port and a second output port connectable to the electromechanical device. Here, the first output port is connected to ground via a ground diode. The driver also includes a high-side power switch, a low-side power switch, and a controller coupled to the high-side power switch and the low-side power switch. Here, the controller is operable in a first mode to charge the solenoid and close the mechanical switch, a second mode to maintain the mechanical switch in a closed state, and a third mode to discharge the solenoid and open the mechanical switch. Also, in the first mode and the second mode, the low-side power switch is in an on state, and the high-side power switch is controlled by the controller to switch between an on state and an off state. As a result, in the on state, a path is formed between the input port and ground via the high-side power switch, the solenoid, and the low-side power switch, and in the off state, a path is formed between ground and ground via the ground diode, the solenoid, and the low-side power switch.

[0008] Optionally, the first mode includes a first stage in which the low-side power switch and the high-side power switch are both in an on state until a target current is reached through the solenoid, and a second stage in which the high-side power switch switches between an on state and an off state to maintain the target current through the solenoid.

[0009] Optionally, the second mode includes a first stage in which the controller operates in an off state to drop the current through the solenoid to a second target value, and a second stage in which the high-side power switch switches between an on state and an off state to maintain the current through the solenoid at the second target value.

[0010] Optionally, during the third mode, the solenoid is discharged via a low-side power switch controlled by a Zener trigger.

[0011] For example, in the third mode, the solenoid is fully discharged and the mechanical switch opens.

[0012] Optionally, a clamp trigger path is provided in parallel with the low-side power switch, the clamp trigger path including a diode, a Zener diode, and a resistor.

[0013] Optionally, the driver is a contactor driver for driving a contactor.

[0014] Optionally, the driver further comprises a multiplexer.

[0015] Optionally, the driver further includes a digital circuit, for example the digital circuit or digital core may be implemented as a state machine.

[0016] Optionally, the digital circuit is adapted to measure a feedback current and update the controller according to the value of the feedback current, for example the feedback current may be the current through a solenoid.

[0017] Optionally, the high-side power switch and the low-side power switch have different voltage ratings. For example, the high-side power switch may have a voltage rating of 45V and the low-side power switch may have a voltage rating of 65V.

[0018] Optionally, the high-side power switch has a voltage rating defined by the battery voltage supplied at the input port.

[0019] Optionally, the low-side power switch has a voltage rating defined by a clamp voltage of the clamp path.

[0020] Optionally, the controller is configured to perform pulse width modulation.

[0021] Optionally, the mechanical switch includes a static contact member and a movable contact member.

[0022] According to a second aspect of the present disclosure, there is provided an electromechanical system including an electromechanical device coupled to a driver of the first aspect.

[0023] According to a third aspect of the present disclosure, there is provided a method for driving an electromechanical device including a solenoid and a mechanical switch, the method comprising: providing a driver including an input port connectable to a battery, a ground port connected to ground, first and second output ports connectable to an electromechanical device, the first output port being connected to ground via a ground diode, a high-side power switch, a low-side power switch, and a controller coupled to the high-side power switch and the low-side power switch; operating the controller in a first mode to charge the solenoid and close the mechanical switch; operating the controller in a second mode to maintain the mechanical switch in a closed state, where in the first and second modes, the low-side power switch is in an on state and the high-side power switch is controlled by the controller to switch between an on state and an off state, such that in the on state, a path is formed between the input port and ground through the high-side power switch, the solenoid, and the low-side power switch, and in the off state, a path is formed between ground and ground through the ground diode, the solenoid, and the low-side power switch; operating the controller in a third mode to discharge the solenoid and open the mechanical switch; Includes.

[0024] Optionally, the second mode includes a first stage in which the controller operates in an off state to drop the current through the solenoid to a second target value, and a second stage in which the controller operates to maintain the current through the solenoid at the second target value.

[0025] The options discussed with respect to the first aspect of the present disclosure are also common to the second and third aspects of the present disclosure. [Brief description of the drawings]

[0026] The present disclosure will now be described in further detail, by way of example only, with reference to the accompanying drawings, in which: [Figure 1A] FIG. 1 shows a driver for driving a contactor according to the prior art. [Figure 1B] FIG. 1B illustrates the circuit of FIG. 1A showing a ground short connection. [Figure 2A] FIG. 2 illustrates the operation of the driver of FIG. 1 during the ON phase. [Figure 2B] FIG. 2 illustrates the operation of the driver of FIG. 1 during the freewheel off phase. [Figure 2C] FIG. 2 illustrates the operation of the driver of FIG. 1 during the clamp-off phase. [Diagram 3] 2 illustrates an alternative embodiment of the driver of FIG. 1. [Figure 4] 4 is a flowchart of a method for driving an electromechanical device according to the present disclosure. [Figure 5A] FIG. 5 illustrates a driver for implementing the method of FIG. [Figure 5B] FIG. 2 is a plot showing current through a solenoid as a function of time. [Figure 6A] FIG. 6 shows the current paths in the ON phase of operation of the circuit of FIG. 5. [Figure 6B] FIG. 2 is a diagram showing the current through the solenoid as a function of time, highlighting the ON operating state in operation. [Figure 6C] FIG. 6 shows the current paths in the circuit of FIG. 5 in the freewheel off state of operation. [Figure 6D] FIG. 2 is a plot showing the current through the solenoid highlighting the freewheel off condition; [Figure 6E] FIG. 6 is a diagram showing a current path in the circuit of FIG. 5 in a clamp-off state; [Figure 6F] FIG. 1 is a plot showing the current through the solenoid, highlighting the clamp-off condition. [Figure 7A] 1A and 1B are diagrams showing the areas that power switches of different configurations occupy on a circuit chip. [Figure 7B] 6 is a diagram showing the area occupied by the power switches of the driver in FIG. 1 in comparison with the area occupied by the power switches of the driver in FIG. 5. [Figure 8A] FIG. 2 is an exploded side view of the contactor. [Figure 8B] FIG. 8B is a side view of the contactor of FIG. 8A. [Figure 9A] FIG. 1 is a diagram illustrating a safe turn-off. [Figure 9B] FIG. 1 illustrates an unsafe turn-off. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] FIG. 1A illustrates a driver for driving an electromechanical device such as a contactor according to the prior art. The driver 100 is coupled to a contactor 110 including a solenoid (load) and a mechanical switch. The driver is adapted to drive the solenoid to actuate the mechanical switch. The driver 100 has an input port connected to a battery having a voltage VBAT, a ground port (CLx) connected to ground, and two output ports CHx and Cox connected to the solenoid of the contactor. The first output port CHx is connected to both the battery and the solenoid.

[0028] Driver 100 includes a digital core 140 coupled to a controller 120 that controls high-side power switches HS1 and HS2 implemented as field effect transistors (FETs) and a low-side power switch LS. A Zener trigger 130 is coupled between the high and low sides of the driver. The Zener trigger turns on the driver in a linear mode and provides a clamp.

[0029] The driver 100 is a high voltage contactor driver that employs both a high voltage clamp and a freewheel path. The high voltage clamp is implemented with a Zener trigger 130 that includes a Zener diode. This allows current to flow in the clamp path only when the voltage at the Zener diode reaches a threshold voltage. In prior art implementations of drivers similar to that shown in FIG. 1A, the clamp was limited to less than 50V, but for high voltage contactors (e.g., automotive contactors), a clamp of up to 60V is required. The driver 100 of FIG. 1A can be implemented with a 60V clamp. The freewheel path of the driver 100 in this embodiment is a switchable freewheel path on the HS side of the driver.

[0030] In this topology, the driver is implemented such that HS1, HS2, and LS are controlled by a controller 120 implemented as a pulse width modulated PWM controller. The PWM controller 120 operates through a digital core 140 adapted to detect feedback currents of both the LS and HS of the driver 100. The values ​​of the feedback currents of the LS and HS of the driver 100 determine the signals that the PWM controller 120 sends to the switches. This particular topology operates in three modes:

[0031] Figures 2A, 2B and 2C show the operation of the circuit of Figure 1. The driver 100 operates in three phases, also called the on-phase, the freewheel-off phase and the clamp-off phase. At 210a, b, c the current through the load as a function of time in each phase is shown, and at 220a, b, c the current path through the driver 100 and the electromechanical device 110 in each phase is shown.

[0032] In the first stage shown in FIG. 2A, a current path is formed from the battery port with voltage VBAT through the electromechanical device 110 and the LS power switch to ground GND. In the initial stage, when the driver is turned on, the LS switch is turned on and the switches HS1 and HS2 are turned off. As the current through the solenoid accumulates, the digital core 140 keeps monitoring its value. When the current exceeds a threshold, the digital core 140 issues a warning to the controller 120 as to when the HS and LS switches are PWM controlled. The time when the PWM control takes over corresponds to the time when the current stops increasing rapidly in the current vs. time plot of 210a. After this time, the driver 100 switches back and forth between two stages including an ON stage and a freewheeling OFF stage. As shown in FIG. 2B, during the freewheeling OFF stage, the PWM control 120 turns off the LS switch and turns on the HS1 and HS2 switches. In this phase, the switchable freewheel path is turned on and the current flows in a circular path including HS1, HS2 and the electromechanical device 110. The HS freewheel path allows the current to be maintained in the load while LS is off. The on and freewheel off phases can be considered as a single operating phase of the driver 100 operating to close the contactor, which is also referred to as turn on (or on) in the following.

[0033] After the contactor is closed, it must immediately open when turned off, and the driver 100 enters the second stage of operation shown in FIG. 2C, the turn-off. When this stage begins, both the HS and LS switches are turned off, and the voltage at the Zener trigger 130 rises until it exceeds a threshold (in this example, the threshold voltage is 60V). At this point, the Zener diode begins to conduct and the clamp path opens, allowing the load to discharge. The driver 100 now enters the third stage, the clamp-off stage. Once the clamp path is opened, the LS switch turns on and begins to operate in linear mode. The output of the circuit is clamped to VDZ above the battery, where VDZ is the threshold voltage of the Zener diode. This clamp allows the load to be de-energized, and the contactor opens. The purpose of switches HS1 and HS2 in driver 100 shown in Figures 1 and 2 is to interrupt the freewheel path during clamping to prevent current from taking the path of least resistance, which would slow de-energize the load and potentially cause contactor welding and damage, which could potentially cause a safety hazard. Driver 100 therefore requires three power switches to operate, two of which are coupled in series with each other, thus increasing the footprint on the circuit chip and increasing manufacturing costs.

[0034] The topology shown in Figure 1A has the disadvantage that if a short circuit to ground occurs on the low side of the driver 100 as shown in Figure 1B, the electromechanical device 110 will still operate since the first output port CHx is directly connected to the battery, which could result in the contactor closing unintentionally, creating a safety concern.

[0035] Figure 3 is an improvement of the driver of Figure 1A. The driver 300 is almost identical to the driver shown in Figure 1, so the same reference numbers are used to indicate the same components. In this case, an additional power switch 310 is coupled between the battery port and the first output port CHx to improve the safety of the system. The power switch 310 turns off the voltage supply from Vbat to CHx in case of a ground short circuit on the low side of the driver 100.

[0036] Adding another power switch to the driver 100 further increases the footprint on the circuit chip. Furthermore, all power switches (HS1, HS2, LS, and 310) need to sustain a high voltage. In the off (clamp) phase, the voltage clamp occurs to the battery to ground path. Therefore, all power switches need to be able to sustain the battery voltage VBAT plus the clamp voltage. In the example of a high voltage contactor, the required clamp voltage is 60V and the minimum required battery voltage is 18V. Therefore, the power switches need to have a voltage rating of at least 80V. This high voltage rating further increases the footprint of the circuit. Adding the power switch 310 to improve the driver safety increases the manufacturing cost.

[0037] The present disclosure seeks to address the issues of chip real estate, manufacturing cost, and safety hazards, while also providing a driver that can quickly de-energize the solenoid to prevent damage to the contactor.

[0038] 4 is a flow chart of a method of driving an electromechanical device according to the present disclosure. The electrochemical device includes a solenoid coupled to a mechanical switch.

[0039] In step 410, a driver is provided. The driver includes an input port connectable to a battery, a ground port connected to ground, and a first output port and a second output port connectable to an electromechanical device. The first output port is connected to ground through a ground diode. The driver further includes a high-side power switch, a low-side power switch, and a controller coupled to the high-side power switch and the low-side power switch.

[0040] In step 420, the controller operates in a first mode to charge the solenoid and close the mechanical switch.

[0041] In step 430, the controller operates in a second mode in which the mechanical switch is kept closed. In the first and second modes, the low-side power switch is in an on state, and the high-side power switch is controlled by the controller to switch between an on state and an off state. In the on state, a path is formed between the input port and ground through the high-side power switch, the solenoid, and the low-side power switch. In the off state, a path is formed between the ground and ground through the ground diode, the solenoid, and the low-side power switch. The off state can be referred to as a freewheel off state in which a low impedance path is formed between the ground and ground.

[0042] In step 440, the controller operates in a third mode to discharge the solenoid and open the mechanical switch.

[0043] Using this approach, the solenoid can be de-energized quickly, allowing the contactors of the mechanical switch to open quickly, thereby extending the life of the contactors.

[0044] FIG. 5A illustrates an electromechanical system including a driver for implementing the method of FIG.

[0045] The electromechanical system 500 includes a driver 520 coupled to an electromechanical device 510, such as a contactor for driving the electromechanical device. The electrochemical device has a mechanical switch 514 and a solenoid 512 coupled to the mechanical switch 514. The driver 520 includes a high-side power switch HS, a low-side power switch LS, and a controller 530 coupled to the high-side power switch and the low-side power switch. The driver 520 has multiple ports including an input port VBATx connectable to a battery (not shown), a ground port CLx connected to ground, and a first output port CHx and a second output port COx connectable to the electromechanical device 510. The first output port CHx is connected to ground via a ground diode D1 (which may be integrated into the device depending on the process technology used).

[0046] The controller 530 may include a digital core 532 coupled to a power switch driver 534 for driving a high side power switch HS and a low side power switch LS. The digital core 532 may be a state machine that initially controls the current to a pull-in threshold and then controls the current to a low hold current level after a pull-in time has elapsed. For example, the digital core may be implemented as in FIG. 1A. The digital current level output of the state machine is the input of a PI controller that regulates the current using PWM.

[0047] The power switch may be implemented in various ways. For example, the power switch may be a field effect transistor (FET). In this implementation, the clamp trigger path 550 is provided between the second output port COx and ground. This connects the clamp trigger path 550 and the low-side power switch LS in parallel. The system 500 may be realized without a clamp path by adding a diode to VBATx to recirculate the current. However, adding a clamp path is advantageous because it allows for faster discharge of the solenoid.

[0048] The clamp trigger path 550 includes diode D2, Zener diode DZ, and resistor R1. In this example topology, the clamp occurs only on the low side of the driver. This means that the two power switches LS and HS do not need to have the same voltage rating. The high-side power switch HS only needs to handle the voltage from the battery VBAT, and the switch LS needs a voltage rating that can handle the clamp voltage.

[0049] For example, the driver 520 may be implemented to operate a high voltage contactor. In this case, a relatively high clamp voltage may be required. In a numerical example, the clamp voltage is 60V and the battery voltage is 40V. This results in voltage ratings of the HS and LS switches of 45V and 65V, respectively. Compared to the driver of FIG. 1, the driver of FIG. 5 has a lower voltage rating for the power switches and fewer power switches are required to safely operate the driver, resulting in a smaller footprint and reduced manufacturing costs.

[0050] The power switch driver 534 may be a pulse width modulated PWM driver. In this example, the PWM driver 534 is operated by a digital core 532 adapted to detect a feedback current in the low-side power switch via a sensor 535. For example, the current sensor may be an ADC sensor. The value of the feedback current determines the signal that the PWM controller 530 sends to the HS switch.

[0051] Optionally, a multiplexer 540 may be provided. In this example, the multiplexer 540 has a first input coupled to the input port VBATx, a second input coupled to the HS power switch, and an output coupled to the digital core 532 via the ADC 536. The multiplexer 540 provides further area reduction since one ADC can be used to measure both the VBAT voltage and the high side current.

[0052] The controller 530 operates in three states or modes including a first mode, also referred to as a pull-in mode, in which the solenoid charges and closes the mechanical switch, a second mode, also referred to as a hold mode, in which the mechanical switch remains closed, and a third mode, also referred to as an off mode, in which the solenoid quickly discharges and opens the mechanical switch.

[0053] FIG. 5B is a plot of the current through the solenoid as a function of time in a first mode (pull-in mode), a second mode (hold mode), and a third mode (off mode).

[0054] The first mode begins when the contactor is first actuated and the driver applies the full battery voltage using a driver-controlled on-state (also called the on-phase) until the pull-in current threshold is reached. The current is then regulated by PWM to conserve power and alternates between the on-state and the off-state or freewheel off-state (also called the freewheel off-phase). The first mode is maintained for a period of time, also called the pull-in time, until the plunger is fully closed, after which the second mode (hold mode) is entered.

[0055] The second mode sets the current level to a lower value, conserving power while keeping the mechanical switch contacts closed. In this mode, the controller regulates the current at a second target level, also called the hold current level, using PWM control that alternates between an on state and a freewheeling off state (also called simply the off state).

[0056] The third mode uses the clamp-off state to quickly de-energize the load.

[0057] FIG. 6 is a diagram for explaining the operation of the system of FIG.

[0058] Figure 6A shows the current path in the on-state of the first mode (pull-in and hold mode of operation), and Figure 6B shows the current through the solenoid, also called the contactor current, as a function of time, highlighting the on-phase during the on-state of operation.

[0059] The current waveform shows times t0 through t7. The first (pull-in) mode occurs between times t0 and t4. The second (hold) mode occurs between times t4 and t6. The third (off) mode occurs twice in the plot, once from the beginning to t0 and once from t6 to the end of the plot.

[0060] At time t0, both the high-side and low-side power switches are turned on and a current path is formed between the input port and ground through the HS switch, the solenoid 512, and the LS switch. The current begins to increase, generating a force on the plunger. The plunger begins to move at t1 generating a back electromotive force (EMF), decreasing the coil current and causing a local maximum at time t1. The current continues to decrease as the plunger moves and abruptly stops when the plunger reaches the end of its travel, shown at time t2 as a local minimum. At this point the mechanical switch is closed and the plunger is fully pulled in. Between times t2 and t3, since there is no longer a back electromotive force, the current increases again and continues until it is limited by the path resistance or reaches a first target current value. The first target current value is a predetermined value defined by the contactor characteristics to ensure pull-in while avoiding unnecessary power dissipation. Digital core 532 maintains this current level by sending a signal to power switch driver 534 to drive the HS power switches with PWM.

[0061] Figure 6C shows the current path during freewheel off operation. Figure 6D shows the current through the solenoid with the freewheel off condition highlighted. In the freewheel off condition, a path is formed between ground and ground through the ground diode, the solenoid, and the low-side power switch.

[0062] During a second mode (hold mode) of operation between times t4 and t6, the controller switches between an on state and a freewheel off state, maintaining the mechanical switch closed. Between t4 and t5, the driver is in the freewheel off state and the current slowly decreases from the first target level to a second target level (also referred to as the hold current level). Once the hold current level is reached, the current is maintained substantially constant at a second target value. The hold current level may be maintained using PWM. The second target value may be a predetermined value defined by the characteristics of the contactor.

[0063] The freewheel path occurs between the diode-to-ground branch D1 and GND, via the solenoid 512 and the low-side power switch LS. In this path, current flows through the solenoid (load), but through a path with low resistance. The presence of the diode D1 means that no additional current is introduced into the circuit path during this mode. The PWM driver 534 switches between the ON and OFF phases / states (freewheel) by switching HS between the ON and OFF states. The current level in the solenoid (load) is maintained, so the solenoid remains energized and the mechanical switch is closed.

[0064] The electromechanical device 510 must then be quickly de-energized to safely open the mechanical switch.

[0065] The third mode begins at time t6, at which the controller operates in the clamp-off state.

[0066] Figure 6E shows the current path during clamp-off operation, and Figure 6F shows the current through the solenoid with the clamp-off condition highlighted.

[0067] A clamp trigger path is formed in parallel with the low-side power switch. The clamp trigger path includes a diode, a Zener diode, and a resistor coupled in series. When the voltage reaches the Zener clamp trigger threshold, the low-side driver is operated in a linear mode. During the clamp off state, the current through the solenoid decreases much faster than in the freewheel off state because the two current paths produce different voltages across the coil.

[0068] Initially, both the HS and LS power switches are off and voltage builds up across Zener diode DZ until it reaches a threshold VDZ (a 60V clamp is required for the high voltage contactor example). Once this threshold is reached, Zener diode DZ begins to conduct, creating a voltage across resistor R1, providing a clamping path that operates the LS transistor in linear mode to allow the load to discharge. The mechanical switch then opens shortly after time t6, around time t7, after the current through the solenoid goes to zero.

[0069] In the third mode, the clamp-off condition, the coil energy is quickly dissipated by a path formed between ground and ground through the ground diode, solenoid, and low-side power switch operating in linear mode with a high clamp voltage from the Zener trigger. The high voltage clamp quickly demagnetizes the coil, so the contacts open quickly, avoiding the drawbacks of a freewheel path or slow demagnetization due to low clamp voltage, and extending the life of the contacts.

[0070] The topology shown in Figure 5 overcomes the shortcomings of the topology shown in Figure 1. If a ground short occurs on the low side of the driver 520, the digital core 532 disables both the HS and LS power switches. In the driver 520, unlike the prior art, the only path from the electromechanical device 510 to the battery is through the HS power switch. Therefore, when the HS is off, no current flows to the load, and the new topology prevents the safety hazard that occurs in the design shown in Figure 1 without requiring an additional power switch.

[0071] The topology shown in Figure 5 and its method of operation (see above) requires only two power switches (HS and LS). In the topology shown in Figure 1, there was a single power switch on the low side, but the freewheel path was on the high side of the driver, and in that topology the freewheel path had to be switchable, so two power switches connected in series were required. Connecting two power switches in series, as shown in Figure 7A, occupies four times the area of ​​a single power switch.

[0072] Figure 7A shows the area occupied on a circuit chip by different configurations of power switches. On the left, 710, shows the area occupied by a single power switch, with only an on-resistance target of Ron. On the right, 720, shows that when two power switches are connected in series, each power switch requires twice the area to meet its on-resistance target, which is four times the area of ​​a single power device.

[0073] Furthermore, in the original topology shown in Figure 1, each power switch had to maintain both the battery voltage and the clamp voltage. If the clamp voltage is 60V and the minimum battery voltage is 18V, then each power switch would have a voltage rating of 80V, and the power switches would occupy a large area on the circuit chip.

[0074] FIG. 7B is a direct comparison of the footprint of the power switches in the original topology 810 of the circuit of FIG. 1 with the footprint of the two power switches in the proposed topology 820 of FIG. 5. In the driver 520, the high-side power switch HS only needs to maintain the battery voltage, and the low-side power switch LS only needs to maintain the clamp voltage. Thus, if the clamp voltage is 60V and the battery load is 40V, the high-side and low-side power switches only need voltage ratings of 45V and 65V, respectively. This lower voltage rating of the power switches means they can be smaller, occupying less real estate on the circuit chip.

[0075] The proposed topology of Figure 5 requires fewer power switches with lower voltage ratings, thus reducing the footprint on the chip and the manufacturing cost of the driver. The proposed design also allows for high voltage clamping and fast de-energization of the electromechanical device, improving safety and preventing damage to the contactors. This driver 520 also has the safety benefit of not tripping the electromechanical device in the event of a ground short circuit.

[0076] Figure 8A is an exploded side view of an electromechanical device consisting of a solenoid and a mechanical switch. The mechanical switch includes a static contact member and a movable contact member. The solenoid has a coil within which resides a plunger (see Figure 8B) coupled to a spring. The spring connects the plunger to the movable contact member.

[0077] When a current flows through the coil, electromagnetic induction occurs. This causes the plunger to exert a force. When this force overcomes the forces of the spring and static friction, the plunger starts to move, drawing the moving contact closer to the static contact. The two contact surfaces then come together, turning the mechanical switch on. By discharging current through the coil, the two contact surfaces can be separated, and the mechanical switch goes to the open position.

[0078] Figure 8B is a side view of the assembled electromechanical device, showing only the solenoid coil and contact block.

[0079] 9A and 9B are diagrams showing current as a function of time, with Fig. 9A illustrating the safe turn-off case as implemented by the embodiments described in this disclosure, and Fig. 9B illustrating the unsafe turn-off case as implemented in the prior art.

[0080] In Figure 9A, it can be seen that when a high voltage clamp circuit is implemented, the energy in the coil is quickly dissipated as shown by the large, sudden drop at the "coil de-energized" point, allowing the mechanical switch contacts to open as quickly as possible.

[0081] In Figure 9B, the unsafe turn-off utilizes only the freewheel path. Current continuously freewheels through the solenoid's coil, causing the coil to slowly de-energize. This can cause multiple opening and closing events of the mechanical switch as the slow movement of the plunger through the coil reverses the direction of the current and causes fluctuating forces on the plunger, as seen by the oscillating line in the lower part of Figure 9B.

[0082] Those skilled in the art will understand that variations of the disclosed arrangements are possible without departing from the present disclosure. Thus, the above description of specific embodiments is for purposes of illustration and not limitation. It will be apparent to those skilled in the art that minor modifications can be made without causing major changes to the operation described above.

Claims

1. 1. A driver for driving an electromechanical device including a solenoid and a mechanical switch, comprising: An input port that can be connected to a battery; A ground port connected to ground; a first output port and a second output port connectable to the electromechanical device, the first output port being connected to ground via a ground diode; A high-side power switch, A low-side power switch; a controller coupled to the high side power switch and the low side power switch; Including, the controller is operable in a first mode to charge the solenoid and close the mechanical switch, a second mode to maintain the mechanical switch closed, and a third mode to discharge the solenoid and open the mechanical switch; In the first mode and the second mode, the low-side power switch is in an on state, and the high-side power switch is controlled by the controller to switch between an on state and an off state, whereby, in the on state, a path is formed between the input port and ground via the high-side power switch, the solenoid, and the low-side power switch, and in the off state, a path is formed between ground and ground via the ground diode, the solenoid, and the low-side power switch. driver.

2. 2. The driver of claim 1, wherein the first mode includes a first stage in which the low-side power switch and the high-side power switch are both in an on state until a target current is reached through the solenoid, and a second stage in which the high-side power switch switches between an on state and an off state to maintain the target current through the solenoid.

3. 2. The driver of claim 1, wherein the second mode includes a first stage in which the controller operates in an off state to drop the current through the solenoid to a second target value, and a second stage in which the high-side power switch switches between an on state and an off state to maintain the current through the solenoid at the second target value.

4. The driver of claim 1 , wherein during the third mode, the solenoid is discharged through the low-side power switch controlled by a Zener trigger.

5. The driver of claim 4 , further comprising a clamp trigger path in parallel with the low-side power switch, the clamp trigger path including a diode, a Zener diode, and a resistor.

6. The driver of claim 1 , which is a contactor driver for driving a contactor.

7. The driver of claim 1 further comprising a multiplexer.

8. The driver of claim 1 further comprising a digital circuit.

9. The driver of claim 8 , wherein the digital circuit is adapted to measure a feedback current and update the controller according to a value of the feedback current.

10. The driver of claim 1 , wherein the high-side power switch and the low-side power switch have different voltage ratings.

11. The driver of claim 1 , wherein the high-side power switch has a voltage rating defined by a battery voltage supplied at the input port.

12. The driver of claim 4 , wherein the low-side power switch has a voltage rating defined by a clamp voltage of a clamp path.

13. The driver of claim 1 , wherein the controller is configured to perform pulse width modulation.

14. The driver of claim 1 , wherein the mechanical switch includes a static contact member and a movable contact member.

15. 10. An electromechanical system comprising an electromechanical device coupled to the driver of claim 1.

16. 1. A method for driving an electromechanical device, including a solenoid and a mechanical switch, comprising: providing a driver including an input port connectable to a battery, a ground port connected to ground, first and second output ports connectable to the electromechanical device, the first output port being connected to ground via a ground diode, a high-side power switch, a low-side power switch, and a controller coupled to the high-side power switch and the low-side power switch; operating the controller in a first mode to charge the solenoid and close the mechanical switch; operating the controller in a second mode to maintain the mechanical switch in a closed state, wherein in the first and second modes, the low-side power switch is in an on state and the high-side power switch is controlled by the controller to switch between an on state and an off state, such that in the on state, a path is formed between the input port and ground via the high-side power switch, the solenoid, and the low-side power switch, and in the off state, a path is formed between ground and ground via the ground diode, the solenoid, and the low-side power switch; operating the controller in a third mode to discharge the solenoid and open the mechanical switch; A method comprising:

17. 17. The method of claim 16, wherein the second mode includes a first stage in which the controller operates in an off state to drop the current through the solenoid to a second target value, and a second stage in which the controller operates to maintain the current through the solenoid at the second target value.

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