Switching circuit, selection circuit, and voltage measuring device

Abstract

Provided is a technique that contributes to the improvement of voltage measurement accuracy and uniform current consumption of a battery in a voltage measurement device. Switch circuits (SWP and SWN) include switch elements (MP1 and MP2 or MN1 and MN2) which are provided between an input terminal and an output terminal, and switch driving units (401 to 409) which are driven between a first power supply voltage (VCC or GND) and a second power supply voltage (GND or VCC), which are different from each other, with an input voltage interposed therebetween. The switch driving unit includes source follower circuits (401 and 404) having a drain side being connected to a first power supply terminal side that is supplied with the first power supply voltage, inputting a voltage based on the input voltage, and supplying a voltage generated in the output side to the switch element as a driving voltage for driving the switch element; and current control units (402 and 405) which open and close a current path between the output side of the source follower circuit and a second power supply terminal being supplied with the second power supply voltage, in response to a control signal (ENABLE).

Description

technical field [0001] The present invention relates to a switching circuit, a selection circuit, and a voltage measurement device, and particularly relates to an effective technology for a voltage measurement device that selects and measures one voltage from a plurality of voltages. Background technique [0002] Currently, electric vehicles (EV: electric vehicle) and hybrid electric vehicles (HEV: hybrid electric vehicle) using electric motors as a driving source for vehicle running are researched and developed by many companies and groups regardless of automobile manufacturers. In order to drive these motors, a vehicle-mounted power supply having a high voltage of several hundred volts is required. The vehicle-mounted power supply described above can be realized by a battery pack in which a plurality of single cells (also referred to as “battery cells”) generating a voltage of about several volts are connected in series. [0003] In electric vehicles, etc., it is necessar...

AI Technical Summary

Problems solved by technology

In addition, the switching element near the lowest position must pass a small current to generate the on-voltage, so the resistance element for generating the on-voltage of the drive circuit (for example, with Figure 19 and Figure 20 The resistance element equivalent to the resistance R) becomes high resistance, resulting in an increase in the area of ​​the voltage measuring device

[0033] The second problem is that the voltage measurement accuracy deteriorates due to the voltage drop caused by the resistance component of the switching element and the signal path, and the driving current of the switching element.

In addition, in order to implement this method with a voltage measuring device, a capacitor element with a large area has to be used, resulting in an increase in circuit scale

[0034] The third problem is that measurement accuracy deteriorates due to an unexpected current leakage path (leak path) occurring in the switching element in the off state

[0035] The fourth issue is the occurrence of measurement errors caused by devices due to the parasitic capacitance of switching elements and offset errors of OP amplifiers in the flying capacitor method voltage measuring device.

In either of Patent Document 5 and Patent Document 9, the processing for correcting errors is complicated, resulting in an increase in circuit scale.

In particular, when an OP amplifier is added as a buffer between the capacitor and the ADC in the flying capacitor circuit as in Patent Document 9, or a sample-and-hold circuit using the OP amplifier is used, the bias of the OP amplifier itself The main factor of the error is the setting voltage, etc.

There are various ways to correct this error, but it may take a lot of work and lead to increased measurement time and power consumption

[0036] In addition, none of the techniques disclosed in Patent Documents 10 to 12 can solve the above problems

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