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US 6,795,321 B2Granted
Method and apparatus for sensing current and voltage in circuits with voltage across an LED
AssigneePower Integrations, Inc.
InventorsBalu Balakrishnan, Arthur B. Odell
Life of this patent
Estimating the term…
Abstract
Methods and apparatuses to sense current and voltage in circuits with voltage drop. A sense circuit includes a series combination of a diode and a resistor in the path of the current to be sensed, the voltage across this series combination coupled to drive a light emitting diode (LED).
Claims30
A circuit, comprising:
- a current sense circuit including a first diode, a first resistor coupled to the first diode and a light emitting diode (LED) coupled to the first diode and the first resistor, the LED is driven in response to a voltage drop across the first diode and the first resistor to sense a first current directed through the first diode and the first resistor;
- and
- a voltage sense circuit coupled across an output of the circuit, the voltage sense circuit including a transistor coupled to the LED;
- the transistor further coupled to a voltage reference, the LED further driven by the transistor in response to a voltage across the output of the circuit.
1 more element
A circuit, comprising:
- a voltage sense circuit coupled across an output, the voltage sense circuit including a voltage reference coupled to the output to drive a base of a bipolar transistor coupled to the output when a voltage across the output exceeds a sense voltage of the voltage sense circuit;
- and
- a compensation circuit including a first resistor coupled to the output and the bipolar transistor, the compensation circuit further including a second resistor, the second resistor coupled between the first resistor and the base of the bipolar transistor such that a sum of a voltage drop across the first resistor and a forward base emitter voltage of the bipolar transistor is to be applied across the second resistor, the sense voltage of the voltage sense circuit varied in response to a current through the second resistor.
The circuit of claim 23 wherein the power supply is a switched mode power supply.
A circuit, comprising:
- a voltage sense circuit coupled across an output, the voltage sense circuit including a first resistor, a zener diode coupled to the first resistor and a light emitting diode of an optocoupler coupled to be driven by the first resistor and the zener diode when a voltage across the output exceeds a sense voltage of the voltage sense circuit, the sense voltage of the voltage sense circuit includes a sum of a voltage drop across the zener diode, a forward voltage of the LED and a voltage drop across the first resistor;
- a current sense circuit coupled to the output, the current sense circuit coupled to provide a voltage representative of a load current supplied from the output;
- and
- a voltage compensation circuit coupled to the current sense circuit and to the voltage sense circuit to vary the voltage drop across the first resistor in response to the voltage representative of a load current supplied from the output.
1 more element
A circuit, comprising:
- a current sense circuit coupled to an output of the circuit, the current sense circuit including,
- a first diode;
- a first resistor coupled to the first diode, the first resistor and first diode coupled to the output such that a load current supplied from the output is directed through the first diode and the first resistor;
- a second resistor coupled to the first resistor and the first diode;
- and
- a light emitting diode coupled to the first resistor and the second resistor and the diode such that the voltage drop across the first resistor and the first diode is coupled to drive the LED;
- a voltage sense circuit coupled to the output and the current sense circuit, the voltage sense circuit including,
- a zener diode coupled to the output;
- a third resistor coupled in series with the zener diode;
- a fourth resistor coupled to the zener diode and the output;
- and
- a bipolar transistor coupled to the LED, the output and the third resistor, the bipolar transistor coupled to drive the LED when a voltage across the output exceeds a sense voltage, the sense voltage including a sum of a voltage drop across the zener diode and a forward base emitter voltage of the bipolar transistor;
- and
- a voltage compensation circuit coupled to the output and the voltage sense circuit, the voltage compensation circuit including,
- a fifth resistor coupled to an emitter of the bipolar transistor and to the output such that a current through the fifth resistor is substantially representative of the load current supplied from the output;
- a sixth resistor coupled to the fifth resistor
- a second diode coupled to the sixth resistor, the sixth resistor and the second diode coupled in series between a base of the bipolar transistor and the fifth resistor such that the sense voltage is varied in response to the current through the fifth resistor.
14 more elements
A circuit, comprising:
- a first diode;
- a first resistor coupled to the first diode, the first resistor and first diode coupled to an output of the circuit such that a a load current supplied from the output is directed through the first diode and the first resistor;
- a second resistor coupled to the first diode and the first resistor;
- a light emitting diode (LED) coupled to the first resistor and the second resistor and the diode such that the voltage drop across the first resistor and the first diode is coupled to drive the LED;
- a third resistor coupled to the output;
- a zener diode coupled to the third resistor and to the LED;
- a bipolar transistor having a collector coupled to the third resistor and the zener diode and a base coupled to the output;
- and
- a fourth resistor coupled between an emitter of the bipolar transistor and the first resistor.
6 more elements
A method, comprising:
- sensing a voltage across an output of a circuit with a voltage sense circuit having a sense voltage that is the sum of a voltage reference and a base emitter voltage drop of a transistor;
- regulating the voltage across the output of the circuit at the sense voltage in a closed loop;
- compensating a voltage drop in a resistor that couples the output of the circuit to a load using a compensation circuit;
- changing the sense voltage with the compensation circuit as a function of a load current supplied by the output of the circuit to compensate for the voltage drop across the resistor;
- and
- canceling substantially the base emitter voltage drop of the transistor with a diode included in the compensation circuit.
3 more elements
Dependencies are inferred from the claim text.