Abstract: In one aspect, a power supply regulator includes a feedback terminal, a node, a control circuit, a first current source, and a second current source. The node is coupled to the feedback terminal to provide a feedback state signal in response to a feedback current through the feedback terminal. The feedback state signal has feedback states that represent an output of the power supply. The control circuit is to be coupled to a power switch and to receive the feedback state signal to regulate the output of the power supply. The first current source is coupled to the node to provide a first current to the node. The second current source is coupled to the node to selectively remove a second current from the node to modulate the feedback current and to alter the feedback state of the feedback state signal.

Abstract: A transient blocking unit (TBU) is a circuit having series-connected transistors that normally conduct current, but automatically switch to a high-impedance current blocking state in response to an over-current condition. Here enhancement mode devices are used in the primary TBU current path, as opposed to the conventional use of depletion mode devices in this context. This approach provides two main advantages. The first advantage is that the dependence of TBU parameters on poorly controlled depletion mode device parameters can be reduced or eliminated. The second advantage is that such TBUs can provide over-voltage protection in addition to over-current protection.

Abstract: An integrated circuit for use in a power supply includes a drive signal generator, a short on time detector, and an oscillator. The drive signal generator generates a drive signal in response to a clock signal. The short on time detector provides an output indicating that consecutive on times of the drive signal are short on times. An on time of the drive signal is a short on time if a switch current of the switch exceeds a current limit after a leading edge blanking period and if the on time of the switch is less than or equal to a sum of the leading edge blanking period and a current limit delay time period. The oscillator generates the clock signal and changes a frequency of the clock signal from a first frequency to a lower second frequency in response to the output of the short on time detector.

Abstract: An example integrated circuit for use in a power supply includes a switch, a terminal and a controller. The controller is coupled to control switching of the switch to regulate the output of the power supply in response to a feedback signal received at the terminal. The controller includes a comparator and an oscillator. The comparator is coupled to detect when a switch current through the switch exceeds a current limit and the oscillator is coupled to extend an off time of the switch in response to the comparator detecting that the switch current exceeds a current limit and if an on time of the switch is substantially equal to a sum of a leading edge blanking period and a current limit delay time period. The oscillator extends the off time of the switch independent of the feedback signal.

Abstract: A variable trip limit transient blocking unit (TBU) is provided. The variable trip limit transient blocking unit circuit includes a transient blocking unit and a low-pass filter, such as an RC circuit having an RC time constant. The RC circuit is disposed to approximate an integrator operating over periods of time that are short compared to the RC time constant. The RC circuit integrates a signal representing an approximated current flowing through the transient blocking unit and triggers a disconnect threshold in the transient blocking unit when a voltage stored across a capacitor of the RC circuit reaches a predefined limit.

Abstract: When a series protective element such as a transient blocking unit (TBU) is used in combination with a shunt protective element such as a gas discharge tube (GDT), firing of the GDT can cause a transient having the potential to damage the TBU. This problem can be alleviated by placing a TBU core in series between depletion mode transistors having their gates connected. With this arrangement, the GDT transient causes a transient in the TBU circuit that has the effect of switching the transistors around the TBU hard off, thereby protecting the TBU from the GDT transient.

Abstract: An example integrated circuit for use in a power supply includes a switch, a terminal and a controller. The controller is coupled to control switching of the switch to regulate the output of the power supply in response to a feedback signal received at the terminal. The controller includes a comparator and an oscillator. The comparator is coupled to detect when a switch current through the switch exceeds a current limit and the oscillator is coupled to extend an off time of the switch in response to the comparator detecting that the switch current exceeds a current limit and if an on time of the switch is substantially equal to a sum of a leading edge blanking period and a current limit delay time period. The oscillator extends the off time of the switch independent of the feedback signal.

Abstract: Techniques are disclosed to limit the current in a switch of a switching power supply. An example switching regulator circuit includes a power switch to be coupled to an energy transfer element of a power supply. A controller to generate a drive signal is coupled to be received by the power switch to control the switching of the power switch. A short on time detector is included in the controller. The short on time detector is to detect an occurrence of a threshold number of one or more consecutive short on times of the switch. A frequency adjuster is also included in the controller and coupled to the short on time detector. The frequency adjuster is to adjust an oscillating frequency of an oscillator included in the controller in response to the short on time detector.

Abstract: In one aspect, a power supply regulator includes a feedback terminal, a node, a control circuit, a first current source, and a second current source. The node is coupled to the feedback terminal to provide a feedback state signal in response to a feedback current through the feedback terminal. The feedback state signal has feedback states that represent an output of the power supply. The control circuit is to be coupled to a power switch and to receive the feedback state signal to regulate the output of the power supply. The first current source is coupled to the node to provide a first current to the node. The second current source is coupled to the node to selectively remove a second current from the node to modulate the feedback current and to alter the feedback state of the feedback state signal.

Abstract: Various techniques directed to the digital control of a switching regulator are disclosed. In one aspect, a power supply regulator includes a compare circuit to be coupled to receive a feedback signal representative of an output level of a power supply. This causes a feedback state signal to be generated having a first feedback state that represents an output level of the power supply that is above a threshold level and a second feedback state that represents an output level of the power supply that is below the threshold level. An adjustment circuit is coupled to the compare circuit to adjust the feedback state signal in response to at least one of adjusting the threshold level or adjusting the feedback signal. The adjustment to the feedback state signal tends to cause the feedback state signal to revert from a state at the time of adjustment to a state immediately preceding the adjustment.

Abstract: Various techniques directed to the digital control of a switching regulator are disclosed. In one aspect, a power supply regulator includes a compare circuit to be coupled to receive a feedback signal representative of an output level of a power supply. This causes a feedback state signal to be generated having a first feedback state that represents an output level of the power supply that is above a threshold level and a second feedback state that represents an output level of the power supply that is below the threshold level. An adjustment circuit is coupled to the compare circuit to adjust the feedback state signal in response to at least one of adjusting the threshold level or adjusting the feedback signal. The adjustment to the feedback state signal tends to cause the feedback state signal to revert from a state at the time of adjustment to a state immediately preceding the adjustment.

Abstract: Digital control of a switching regulator in one aspect includes a compare circuit to be coupled to receive a feedback signal representative of an output level of a power supply. A feedback state signal is generated having a first feedback state and a second feedback state. An adjustment circuit is coupled to the compare circuit to adjust the feedback state signal in response to at least one of adjusting the threshold level or adjusting the feedback signal. The adjusted feedback state signal causes the feedback state signal to revert from a state at the time of adjustment to a state immediately preceding the adjustment. A control circuit is to be coupled to a power switch and is to be coupled to receive an oscillating signal and the feedback state signal.

Abstract: A transient blocking unit (TBU) is a circuit having series-connected transistors that normally conduct current, but automatically switch to a high-impedance current blocking state in response to an over-current condition. Here enhancement mode devices are used in the primary TBU current path, as opposed to the conventional use of depletion mode devices in this context. This approach provides two main advantages. The first advantage is that the dependence of TBU parameters on poorly controlled depletion mode device parameters can be reduced or eliminated. The second advantage is that such TBUs can provide over-voltage protection in addition to over-current protection.

Abstract: A transient blocking unit (TBU) is an arrangement of two or more transistors connected to each other in series such that they automatically switch off when a TBU current passing through these transistors exceeds a predetermined threshold. Voltage turnoff capability is provided for a TBU by adding a voltage comparison circuit to the TBU. The voltage comparison circuit provides gate voltages to one or more of the TBU transistors that tend to turn off the TBU transistors, if the voltage at the TBU output (i.e., the protected device output voltage) falls outside a predetermined range. The voltage provided by the voltage comparison circuit adds constructively to the gate voltages provided by normal TBU operation. Accordingly, TBU switch off can be driven by an over-current condition (TBU current out of range) and/or by an over-voltage condition (TBU output voltage out of range).

Abstract: Techniques are disclosed to limit the current in a switch of a switching power supply. An example switching regulator circuit includes a power switch to be coupled to an energy transfer element of a power supply. A controller to generate a drive signal is coupled to be received by the power switch to control the switching of the power switch. A short on time detector is included in the controller. The short on time detector is to detect an occurrence of a threshold number of one or more consecutive short on times of the switch. A frequency adjuster is also included in the controller and coupled to the short on time detector. The frequency adjuster is to adjust an oscillating frequency of an oscillator included in the controller in response to the short on time detector.

Abstract: A current-limiting surge protection device is provided. The current-limiting surge protection device includes a pair of series connected normally on MOSFET's and a pair of voltage controlled normally off switches that are disposed to monitor a voltage across the normally on MOSFET pair. Here, the voltage controlled normally off switches close according to an excess threshold voltage across the MOSFET pair and reduces a gate drive potential of the normally on MOSFET pair to limit a current through the normally on MOSFET pair.

Abstract: Techniques are disclosed to limit the current in a switch of a switching power supply. An example switching regulator circuit includes a power switch to be coupled to an energy transfer element of a power supply. A controller to generate a drive signal is coupled to be received by the power switch to control the switching of the power switch. A short on time detector is included in the controller. The short on time detector is to detect an occurrence of a threshold number of one or more consecutive short on times of the switch. A frequency adjuster is also included in the controller and coupled to the short on time detector. The frequency adjuster is to adjust an oscillating frequency of an oscillator included in the controller in response to the short on time detector.

Abstract: An isolation device having normally off detection is provided. The isolation device having normally off detection includes a transient blocking unit (TBU) having at least one depletion mode device disposed between a pair of sense terminals, and at least one normally off transition element disposed to drive a gate of the depletion mode device in the TBU, where the normally off transition element transitions from a first resistive state to a second resistive state and one depletion mode device is connected to one sense terminal, and the normally off transition element transitions by detection of a current through the TBU. The TBU can be unidirectional or bidirectional.

Abstract: When a series protective element such as a transient blocking unit (TBU) is used in combination with a shunt protective element such as a gas discharge tube (GDT), firing of the GDT can cause a transient having the potential to damage the TBU. This problem can be alleviated by placing a TBU core in series between depletion mode transistors having their gates connected. With this arrangement, the GDT transient causes a transient in the TBU circuit that has the effect of switching the transistors around the TBU hard off, thereby protecting the TBU from the GDT transient.

Abstract: A transient blocking unit (TBU) is a transistor circuit that is normally on, but rapidly and automatically switches to a high-resistance current blocking state when a current threshold is exceeded, thereby protecting a series connected load from over-voltage or over-current conditions. Process variation of transistor threshold voltage and on-resistance can cause undesirable variation of the TBU threshold current and/or of TBU resistance. Control of TBU threshold current and/or resistance is improved by providing for trimming the TBU during its fabrication to provide a one-time adjustment of the threshold current or resistance. Such trimming can be done with a resistive trimming circuit placed in series with the on-resistance of the relevant TBU transistor. Alternatively, a segmented TBU transistor having an on-resistance that is adjustable by way of wire bonding during fabrication can be employed.