An auxiliary power supply circuit operating within a wide input voltage range has a voltage follower unit and a voltage comparison unit. The voltage follower unit has an electronic switch, a resistor, and a Zener diode. The electronic switch has a first terminal electrically connected to a voltage input terminal of the working voltage conversion circuit, a second terminal electrically connected to a voltage output terminal of the working voltage conversion circuit, and a control terminal. The resistor is electrically connected between the first terminal and the control terminal of the electronic switch. The Zener diode has a cathode electrically connected to the control terminal of the electronic switch. The voltage comparison unit has a detecting terminal electrically connected to the voltage input terminal of the working voltage conversion circuit, and an output terminal electrically connected to the control terminal of the electronic switch.

A switch apparatus is provided. The switch apparatus includes a signal control switch, a switch circuit, a blocking capacitor and a surge current dissipation circuit. The signal control switch and the switch circuit are respectively controlled by a first control signal and a second control signal to be turned on or off. The blocking capacitor is serially coupled between the switch circuit and a reference voltage end. The surge current dissipation circuit includes a Zener diode circuit or at least one diode circuit, and the at least one diode circuit has one or more diodes coupled in series. The one or more diodes coupled in series are coupled between two ends of the surge current dissipation circuit according to a first polarity direction.

In a first aspect, the subject invention provides a variable-intensity light emitting diode (LED) module which includes: a first LED string having first and second ends, the first end being connected to a positive voltage terminal which is connectable to a positive voltage input of a direct current voltage source; a first terminal connected to a first resistor which is connected to the second end of the first LED string; and, a second terminal connected to a second resistor which is connected to the second end of the first LED string. The first and second resistors have different resistances. A negative voltage input of the direct current voltage source is selectively connectable to one of the first and second terminals, whereby, the intensity of light generated by the first LED string is determined by which of the first and second terminals is connected to the negative voltage input.

A power supply circuit that outputs via an output terminal an output voltage based on an input voltage applied to an input terminal includes: an inserted transistor of an N-channel depletion type inserted between the input terminal and an internal supply power terminal; and a regulator configured to generate the output voltage by using as a supply voltage a voltage applied to the internal supply power terminal. The gate of the inserted transistor is connected to the output terminal.

An integrated circuit includes a voltage reference circuit including a Zener diode having a first terminal coupled to a first node and a second terminal coupled to a first voltage supply terminal. A proportional to absolute temperature (PTAT) circuit is coupled at the first node and configured to generate a PTAT current. A PTAT compensation circuit is coupled at the first node. The PTAT compensation circuit includes a first current mirror having a first branch coupled at the first node.

An electronic device includes a voltage regulator circuit having a power NFET coupled between an upper supply voltage and a pre-regulator output node and a current source coupled in series with a diode element between the upper supply voltage and a lower supply voltage. A gate of the power NFET is coupled to a first node between the current source and a diode element. A bypass circuit includes a power PFET coupled between the upper supply voltage and the pre-regulator output node. A comparison circuit is coupled to turn the bypass circuit off when the upper supply voltage is greater than a regulation threshold voltage.

An electronic device includes a voltage regulator circuit having a power NFET coupled between an upper supply voltage and a pre-regulator output node and a current source coupled in series with a diode element between the upper supply voltage and a lower supply voltage. A gate of the power NFET is coupled to a first node between the current source and a diode element. A bypass circuit includes a power PFET coupled between the upper supply voltage and the pre-regulator output node. A comparison circuit is coupled to turn the bypass circuit off when the upper supply voltage is greater than a regulation threshold voltage.

Provided is a reference voltage circuit including a Zener diode having a cathode connected to a current source via a first node, and an anode connected to a ground point; a first resistor having one end connected to the first node; a second resistor having one end connected to another end of the first resistor; a first diode having an anode connected to another end of the second resistor via a second node, and a cathode connected to the ground point; and a current control circuit configured to generate a control current corresponding to an anode voltage of the first diode so that the current source supplies a reference current corresponding to the control current to the first diode.

A current mirror arrangement with a current mirror and a double-base current circulator is disclosed. The current mirror is configured to receive an input current (I.sub.IN) and generate a mirrored current (IM), where IM=K*I.sub.IN. The current circulator, coupled to the current mirror, is configured to convey the mirrored current to an output node of the arrangement. The current circulator is a double-base current circulator and includes a first branch configured to receive a first branch current (I1b), where I1b=m*IM, where m is a positive number less than 1, and further includes a second branch configured to receive a second branch current (I2b), where I2b=(1m)*IM. The first branch includes a cascode of transistors Q3 and Q5, configured to provide I1b to an output node. The second branch includes a transistor Q4 configured to provide I2b to the output node, where it is combined with I1b.

In a first aspect, the subject invention provides a variable-intensity light emitting diode (LED) module which includes: a first LED string having first and second ends, the first end being connected to a positive voltage terminal which is connectable to a positive voltage input of a direct current voltage source; a first terminal connected to a first resistor which is connected to the second end of the first LED string; and, a second terminal connected to a second resistor which is connected to the second end of the first LED string. The first and second resistors have different resistances. A negative voltage input of the direct current voltage source is selectively connectable to one of the first and second terminals, whereby, the intensity of light generated by the first LED string is determined by which of the first and second terminals is connected to the negative voltage input.