# US 11,079,416 B2 · Voltage monitoring apparatus > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,079,416 B2 - Document ID: US11079416B2 - Status: Granted - Kind: B2 - Application number: 16/844,381 - Filed: 2020-04-09 - Published: 2020-10-15 - Granted: 2021-08-03 - Earliest claimed: 2019-04-11 - Assignees: Rohm Co., Ltd. - Applicants: Rohm Co., Ltd. - Inventors: Fumihiko Terasaki - Web page: https://patentgrep.com/patent/US11079416B2 ## CPC - G01R 19/16504: {characterised by the components employed} - G01R 19/16519: {using FET's} - G01R 19/16576: {comparing DC or AC voltage with one threshold (G01R19/16514, G01R19/16519, G01R19/16528, G01R19/16533 and G01R19/1659 take precedence)} - H03K 5/084: {modified by switching, e.g. by a periodic signal or by a signal in synchronism with the transitions of the output signal} - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) - H03K: PULSE TECHNIQUE (measuring pulse characteristics G01R; modulating sinusoidal oscillations with pulses H03C; transmission of digital information H04L; discriminator circuits detecting phase difference between two signals by counting or integrating cycles of oscillation H03D3/04; automatic control, starting, synchronisation or stabilisation of generators of electronic oscillations or pulses where the type of generator is irrelevant or unspecified H03L; coding, decoding or code conversion, in general H03M) ## Abstract The present invention provides a voltage monitoring apparatus capable of stable operation even in a low-voltage region. The voltage monitoring apparatus (1) includes: an inner voltage generating portion (40), lowering an input voltage (VIN) to generate an inner voltage (Vreg); an input voltage monitoring portion (30), receiving a power supply from an output terminal of the inner voltage generating portion (40) to operate; a switch portion (50), disposed between an input terminal of the input voltage (VIN) and the output terminal of the inner voltage generating portion (40); and a switch driving portion (60), turning on the switch portion (50) when the input voltage (VIN) is lower than a threshold voltage (for example, VyVref). Furthermore, the threshold voltage is preferably set as, for example, turning off the switch portion (50) upon the inner voltage generating portion (40) changing to a state capable of outputting the inner voltage (Vreg) that is at least higher than a minimum operating voltage of the input voltage monitoring portion (30). ## Claims ### Claim 1 A voltage monitoring apparatus, comprising: an inner voltage generating portion, lowering an input voltage to generate an inner voltage; an input voltage monitoring portion, receiving a power supply from an output terminal of the inner voltage generating portion to operate; a switch portion, disposed between an input terminal of the input voltage and the output terminal of the inner voltage generating portion; and a switch driving portion, turning on the switch portion when the input voltage is lower than a threshold voltage and turning off the switch portion when the input voltage is higher than the threshold voltage. ### Claim 2 (depends on 1) The voltage monitoring apparatus according to claim 1, wherein the threshold voltage is set as: turning off the switch portion upon the inner voltage generating portion changing to a state of being capable of outputting the inner voltage at least higher than a minimum operating voltage of the input voltage monitoring portion. ### Claim 3 (depends on 1) The voltage monitoring apparatus according to claim 1, wherein the threshold voltage is set as: turning off the switch portion before the input voltage exceeds a withstand voltage of the input voltage monitoring portion. ### Claim 4 (depends on 2) The voltage monitoring apparatus according to claim 2, wherein the threshold voltage is set as: turning off the switch portion before the input voltage exceeds a withstand voltage of the input voltage monitoring portion. ### Claim 5 (depends on 1) The voltage monitoring apparatus according to claim 1, wherein the switch portion comprises: a PMOSFET (p-channel metal-oxide-semiconductor field-effect transistor), comprising a source connected to the input terminal of the input voltage, and a drain connected to the output terminal of the inner voltage generating portion; an NMOSFET (n-channel metal-oxide-semiconductor field-effect transistor), comprising a drain connected to a gate of the PMOSFET, a source connected to a ground terminal, and a gate connected to the switch driving portion; and a current source, comprising a first terminal connected to the input terminal of the input voltage, and a second terminal connected to a gate of the PMOSFET. ### Claim 6 (depends on 5) The voltage monitoring apparatus according to claim 5, wherein the threshold voltage is set as: turning off the NMOSFET before the input voltage exceeds a gate-source withstand voltage of the PMOSFET. ### Claim 7 (depends on 1) The voltage monitoring apparatus according to claim 1, wherein the input voltage monitoring portion comprises: a first comparator, receiving the power supply from the output terminal of the inner voltage generating portion to operate, and comparing a first divided voltage corresponding to the input voltage with a predetermined reference voltage to generate a first comparison signal; and an output transistor, turning on/off according to the first comparison signal. ### Claim 8 (depends on 7) The voltage monitoring apparatus according to claim 7, wherein the input voltage monitoring portion further comprises: a delay portion, providing the first comparison signal with a delay. ### Claim 9 (depends on 7) The voltage monitoring apparatus according to claim 7, wherein the switch driving portion comprises: a second comparator, receiving the power supply from the output terminal of the inner voltage generating portion to operate, and comparing a second divided voltage corresponding to the input voltage with the reference voltage to generate a second comparison signal for driving the switch portion. ### Claim 10 (depends on 8) The voltage monitoring apparatus according to claim 8, wherein the switch driving portion comprises: a second comparator, receiving the power supply from the output terminal of the inner voltage generating portion to operate, and comparing a second divided voltage corresponding to the input voltage with the reference voltage to generate a second comparison signal for driving the switch portion. ### Claim 11 (depends on 9) The voltage monitoring apparatus according to claim 9, further comprising: a divided voltage generating portion, dividing the input voltage to generate the first divided voltage and the second divided voltage. ### Claim 12 (depends on 11) The voltage monitoring apparatus according to claim 11, wherein the divided voltage generating portion adjusts a voltage divider ratio of at least one of the first divided voltage and the second divided voltage.