# US 2019/0170803 A1 · Sensing resistor short determiner, switch control circuit including the same and power supply including the switch control circuit

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- Number: US 2019/0170803 A1
- Document ID: US20190170803A1
- Status: Published application
- Kind: A1
- Application number: 16/266,194
- Filed: 2019-02-04
- Published: 2019-06-06
- Earliest claimed: 2013-12-12
- Assignees: Semiconductor Components Industries, LLC
- Applicants: Semiconductor Components Industries, LLC
- Inventors: In-Ki PARK; Hyun-Chul EUM; Yong-Sang SHIN
- Web page: https://patentgrep.com/patent/US20190170803A1

## CPC

- G01R 31/40: Testing power supplies (testing photovoltaic devices H02S50/10)
- G01R 31/52: Testing for short-circuits, leakage current or ground faults
- H02M 3/33507: {with automatic control of the output voltage or current, e.g. flyback converters (H02M3/33561, H02M3/33569 take precedence)}
- H03K 17/0822: {in field-effect transistor switches}
- G01R 1/203: {Resistors used for electric measuring, e.g. decade resistors standards, resistors for comparators, series resistors, shunts (resistors in general H01C; microwave or radiowave terminations H01P1/26; coupling devices H01R)}
- H02M 1/0009: {Devices or circuits for detecting current in a converter}
- H02M 1/32: Means for protecting converters other than automatic disconnection
- H03K 2217/0027: Measuring means of, e.g. currents through or voltages across the switch
- G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12)
- H02M: APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF (transformers H01F; dynamo-electric converters H02K47/00; controlling transformers, reactors or choke coils, control or regulation of electric motors, generators or dynamo-electric converters H02P)
- 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

According to the exemplary embodiments, a short-circuit of a sense resistor is detected according to a result of comparison between a sense voltage and a reference voltage at a time based on at least one of a period set based on an input sense voltage and a turn-on time of a power switch. A blanking period is set based on the input sense voltage in a current mode, and a short-circuited resistor detection period is set based on the input sense voltage.

## Claims

### Claim at position 1

1-24. (canceled)

### Claim 25

A short-circuit detection circuit, comprising:
an input voltage detector circuit configured to detect an input voltage coupled to a power switch and to generate an input sense voltage according to the input voltage;
a sense voltage comparator circuit configured to compare a sense voltage and a reference voltage to generate a comparison signal, the sense voltage being generated by a current that flows from the input voltage through the power switch and a sense resistor when the power switch is turned; and
a blanking period setting circuit configured to assert a blanking signal when the power switch is on, wherein the blanking period setting circuit determines a duration of the blanking signal according to the input sense voltage,
wherein the short-circuit detection circuit is configured to:
not detect a short-circuit of the sense resistor when the blanking signal is asserted, and
detect the short-circuit of the sense resistor according to the comparison signal when the blanking signal is not asserted and the power switch is on.

### Claim 26 (depends on 25)

The short-circuit detection circuit of claim 25, wherein the assertion of the blanking signal is synchronized to a turn-on time of the power switch.

### Claim 27 (depends on 26)

The short-circuit detection circuit of claim 26, wherein the duration of the blanking signal is decreased in response to an increase in the input sense voltage and is increased in response to a decrease in the input sense voltage.

### Claim 28 (depends on 25)

The short-circuit detection circuit of claim 25, wherein the short-circuit detection circuit is configured to not detect a short-circuit of the sense resistor when the power switch is off.

### Claim 29 (depends on 25)

The short-circuit detection circuit of claim 25, further comprising:
a signal generator circuit that asserts a short-circuit detection signal in response to a rising edge of a shut-down signal,
wherein the short-circuit detection circuit is configured to assert the shut-down signal in response to detecting the short-circuit of the sense resistor.

### Claim 30 (depends on 25)

The short-circuit detection circuit of claim 25,
wherein the input voltage is coupled to the power switch through a first coil of a transformer, and
wherein the input sense voltage is generated using a current generated by a second coil of the transformer.

### Claim 31 (depends on 25)

The short-circuit detection circuit of claim 25,
wherein the input sense voltage is generated using a voltage produced by a voltage divider coupled to the input voltage.

### Claim 32 (depends on 25)

The short-circuit detection circuit of claim 25, wherein the short-circuit detection circuit is configured to:
not detect the short-circuit of the sense resistor during an interval after the power switch is turned on and before a determination to turn off the power switch; and
detect the short-circuit of the sense resistor according to the comparison signal when the blanking signal is not asserted during the interval after the determination to turn off the power switch and before the power switch is turned off.

### Claim 33 (depends on 32)

The short-circuit detection circuit of claim 32, further comprising:
a peak detector signal to determine a peak voltage of the input sense voltage; and
a peak reference generator circuit to determine a peak reference voltage according to the determined peak voltage, the peak reference voltage being less than the peak voltage,
wherein the blanking period setting circuit asserts the blanking signal when the power switch is on and the input sense voltage is greater than the determined peak reference voltage, and de-asserts the blanking signal when the power switch is off or the input sense voltage is less than the determined peak reference voltage.

### Claim 34

A short-circuit detection circuit, comprising:
a blanking period setting circuit configured to receive an input sense voltage and produce a blanking signal having an asserted duration determined using the input sense voltage;
a first comparator circuit configured to compare a sense voltage to a reference voltage and assert a comparison signal when the sense voltage is less than the reference voltage; and
an AND gate configured to receive the blanking signal, the comparison signal, and a gate control signal and to assert a shut-down signal when the blanking signal is asserted, the comparison signal is asserted, and the gate control signal is asserted,
wherein the gate control signal being asserted indicates a power switch is turned on.

### Claim 35 (depends on 34)

The short-circuit detection circuit of claim 34, wherein the asserted duration of the blanking signal is synchronized to the assertion of the gate control signal.

### Claim 36 (depends on 35)

The short-circuit detection circuit of claim 35, wherein the blanking period setting circuit is configured to increase the asserted duration when the input sense voltage decreases and to decreases the asserted duration when the input sense voltage increases.

### Claim 37 (depends on 34)

The short-circuit detection circuit of claim 34, further comprising:
a signal generator circuit that asserts a short-circuit detection signal in response to a rising edge of a shut-down signal.

### Claim 38 (depends on 34)

The short-circuit detection circuit of claim 34, wherein the blanking period setting circuit comprises:
a peak detector signal to determine a peak voltage of the input sense voltage; and
a peak reference generator circuit to determine a peak reference voltage according to the determined peak voltage, the peak reference voltage being less than the peak voltage,
a second comparator circuit configured to compare the input sense voltage to the peak reference voltage and assert the blanking signal when the input sense voltage is greater than the peak reference voltage.

### Claim 39 (depends on 34)

The short-circuit detection circuit of claim 34, further comprising:
an input voltage detector circuit to produce the input sense voltage according to an input voltage coupled to the power switch.

### Claim 40

A method for detecting a short circuit, the method comprising:
determining, using an input voltage detector circuit, an input sense voltage corresponding to an input voltage coupled to a power switch;
generating, using a blanking period setting circuit, a blanking signal having an asserted duration determined using the input sense voltage;
determining, using a sense voltage comparator circuit, whether a sense voltage is less than a reference voltage;
determining whether the power switch is turned on; and
asserting a shut-down signal in response to the sense voltage being less than the reference voltage when the blanking signal is not asserted and the power switch is turned on,
wherein the sense voltage is generated using a sense resistor coupled in series with the power switch.

### Claim 41 (depends on 40)

The method of claim 40, wherein the assertion of the blanking signal is synchronized to the power switch being turned on.

### Claim 42 (depends on 41)

The method of claim 41, wherein the asserted duration of the blanking signal is decreased in response to an increase in the input sense voltage and is increased in response to a decrease in the input sense voltage.

### Claim 43 (depends on 40)

The method of claim 40, further comprising:
asserting a short-circuit detection signal in response to a rising edge of a shut-down signal.

### Claim 44 (depends on 40)

The method of claim 40, further comprising:
determining a peak voltage of the input sense voltage;
determining a peak reference voltage using the determined peak voltage, the peak reference voltage being less than the peak voltage;
asserting the blanking signal when the input sense voltage is greater than the determined peak reference voltage; and
de-asserting the blanking signal when the input sense voltage is less than the determined peak reference voltage.