Abstract:
A method of converting a periodic pulse width modulated input signal into a voltage output signal wherein the input signal is in an active state for a first portion of each of successive time periods and in an inactive state for a second portion of each time period. A first and second input is supplied to an integrator circuit and a first capacitor is coupled between a first output of the integrator circuit and the first input and a second capacitor is coupled between a second output and the second input of the integrator circuit during a first time period of the pulse width modulated signal. A third capacitor is coupled between a first output of the integrator circuit and the first input and a fourth capacitor is coupled between a second output of the integrator circuit and the second input during a successive second time period of the pulse width modulated signal. Said coupled capacitors are charged during the active state of the first and second time periods and discharged during the inactive state of the first and second time periods.
Abstract:
A circuit for providing a control signal for a load includes a first switch having a first and a second state, a second switch having a first and a second state coupled to said first switch, a load connected to said first and second switches, protection circuitry for protecting said load from excessive voltage and circuitry for switching said first switch. The circuit is arranged so that when the first switch is in the first state current flows from the load to the first switch and the switching circuitry is arranged to switch the first switch to the second state when the voltage across the load reaches a predetermined value.
Abstract:
A differential amplifier circuit comprises: an amplifying section including first and second current branches and an output stage which comprises a current sinking element and a control element. The circuit also includes a current limiting section which comprises a current detecting element connected to detect the current through the current sinking element and arranged to drive the current limiting element when the detected current exceeds a predetermined threshold to inject current at the collector of the transistor in the first current branch.
Abstract:
A battery charger is provided which has a power output to charge a battery. The battery charger comprises a power input and a circuit for determining a temperature at the battery charger. The battery charger further includes a controller which varies the power output among a plurality of non-zero power levels in dependence upon the difference between the determined temperature and a reference temperature.
Abstract:
A voltage converter comprises an input, an output and a current control arrangement for controlling the output current of the voltage converter circuit. The current control arrangement comprises a first mode, when the voltage output by the converter circuit is above a threshold voltage, and a second mode in which the voltage output by the circuit is below the threshold voltage. The first and second modes are controlled by the same current control arrangement. The current control arrangement comprises comparing means arranged to receive a reference voltage wherein the reference voltage is a voltage offset associated with at least one of the inputs of the comparing means.
Abstract:
A method of converting a periodic pulse width modulated input signal into a voltage output signal wherein the input signal is in an active state for a first portion of each of successive time periods and in an inactive state for a second portion of each time period. A first and second input is supplied to an integrator circuit and a first capacitor is coupled between a first output of the integrator circuit and the first input and a second capacitor is coupled between a second output and the second input of the integrator circuit during a first time period of the pulse width modulated signal. A third capacitor is coupled between a first output of the integrator circuit and the first input and a fourth capacitor is coupled between a second output of the integrator circuit and the second input during a successive second time period of the pulse width modulated signal. Said coupled capacitors are charged during the active state of the first and second time periods and discharged during the inactive state of the first and second time periods.
Abstract:
There is provided a controller for a DC motor drive transistor which controls a parameter of a motor, the transistor being of PNP or NPN type, and the controller comprising a detection circuit, adapted to determine whether the DC motor drive transistor is of the PNP or NPN type and a driver circuit, adapted to sink current from the PNP transistor if it is determined that a PNP transistor is present, or source current into the NPN transistor if it is determined that an NPN transistor is present.
Abstract:
A circuit is used in the output stage of an operational amplifier which allows a rail to rail swing of the output voltage while consuming low quiescent power. The circuit includes first and second control elements each having a controllable path and a control node. The circuit further includes a third control element having a controllable path connected between the control nodes of the first and second control elements via a resistive path. A voltage indicative of an input signal is applied to a node of the resistive path. Current flow through the controllable paths of the first and second control elements changes in response to changes in the voltage at the node. More specifically, current flow through the controllable path of the second control element changes in dependance on the current flow through the controllable path of the third control element. Additionally, as one of the first and second control elements is turned on, the other control element is held off.
Abstract:
A current source, adapted to generate a current proportional to absolute temperature has a greatly reduced supply voltage dependence and is still able to operate at low operating voltages. This is achieved by the incorporation of a compensation resistor through which a start-up current is passed.
Abstract:
A current source circuit is described for generating control current. The circuit is capable of generating a very accurate reference current and in particular dealing with the problem which can arise from injected noise. A feedback loop is implemented to reject the charge injection noise.