TWI311402B - Differential load driver circuits - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a differential load driving circuit, and more particularly to a pulse width modulation when operating in a linear mode and a high current demand for a low current demand. Differential load drive circuit in variable (PWM) mode. [Prior Art] Pulse Width Modulation (PWM) technology is often used in high-power electronic devices to drive large load currents because of its efficiency. In comparison, linear current is hardly used for large load currents due to its low efficiency. However, since there is no switching signal in the linear current source, there is no chopping of the output current. The PWM drive load current inevitably has some current ripple, and the amplitude of the ripple depends on the cutoff frequency and attenuation of the filter circuit. Usually four power metal oxide semiconductor field effect transistors Oxide Semiconductor Field Effect D (10) 仏 (10), abbreviated as MOSFET) are connected into an H-bridge circuit to drive the differential load, and Figures 2 and 2 represent the H used to drive a load. - Bridge circuit. It is known to those skilled in the art that the H-bridge circuit in the figure includes four switches (12, 14, 丨6 and ^) arranged as shown to drive the load 19. The current flow in Figure 1 is from left to right. Defined as "cooling n (c〇〇Un magic direction. In Figure 2, the current flow direction is defined here from right to left as "heating" in the direction of (10). Figure 1, Figure 2 shows driving in heating and cooling mode 4 A 1^-bridge-connected power MOSFET is used to drive the signal required for the resistive load. For example, to drive in cooling mode (Figure υ negative 胄, PWM signal is applied to ^ and N1 ' and P2 is off and = fully Turn on 'its work is similar to our familiar

O:\9I\9I037DOC 1311402 Learned BUCK buck converter. The duty cycle of the pwM signal is to control the current ripples through the resistive load 'Red, Cl, L2, and C2' to reduce the current ripple through the load. Each switch has a corresponding pre-driver circuit (not turned out) so that it can be turned off with a suitable potential drive (4). Such a design encounters some problems when the load requires low current flow. In the case of low current, the duty cycle of the PWM signal is correspondingly reduced. In any case, the drive capability of the pre-driver circuit is limited by the duty cycle, and the gate input capacitance of the power MOSFET is large. Therefore, it is impossible to drive these power MOSFETs with very small duty cycle signals, resulting in a small load current that cannot be output in the heating or cooling mode. At the same time, because the average DC value of the load current decreases, the percentage of current chopping relative to the output DC current is greatly increased. Figures 3 and 4 show another circuit of the variation of Figures 1 and 2, which removes a set of filter circuits L2 and C2, which generally saves cost and reduces volume. However, in the case of low output current, such a circuit has problems such as the increase of chopping in the figure 〖, Fig. 2. SUMMARY OF THE INVENTION In one aspect, the present invention provides an H-bridge load driving circuit including: four power switches forming a Η-bridge circuit, the power switch being selectively connected to a load and supplying current to the load; A current source; wherein the circuit can be connected to a power switch or current source to the load as a function of load current. In another aspect, the present invention provides a differential load driving circuit comprising: a plurality of power supplies that are connected to a load and provide current to the load.

O:\91\9I037 OOC 1311402 off; multiple power switch drive circuits 'the power switch drive circuit controls the conduction state of the power switch' and selectively connects the two of the plurality of power switches to - two pulse width adjustments Variable signal; and at least one current source. The electric μ source., the load phase is connected' and supplies current to the load when the load is in a low current state. The pulse width modulation signal is connected to the load and supplies current to the load when the load is in a high current state. In addition, the invention provides a bridge load drive circuit comprising: four power switches forming an H-bridge circuit, the power switch being selectively connected to a load to supply current to the load; and a plurality of power switch drive circuits, the power switch The driving circuit controls an on state of the power switch, and selectively connects at least one of the plurality of power switches to the pulse width modulation signal; and at least one current source. The bridge circuit has a first mode and a second mode. In the first mode, the current source is connected to the load to supply current to the load, and in the second mode, the Φ / field in the power switch, y, '^ two are connected to the pulse The width modulation signal provides the load current to the load. θ In addition, the present invention provides a circuit for differentially driven thermoelectric cooler (Thermal, abbreviated as TEC), which comprises: selectively connecting to a thermoelectrically cooled 芎 恭 么 &#& π load for the load 耠 supply current a power switch; a plurality of power switch drive circuits 'a power switch drive circuit controls an on state of the power switch' and selectively connects at least one of the plurality of power switches to a pulse width modulation signal; and at least one current source . Bad eight

The load driving circuit has a first mode and a second mode, and at least two of the first to the current source are connected to the load to supply the load, and at least two are connected to the pulsed wide power supply switch. negative

〇\91\9t037 OOC 1311402 Current. It is to be understood by those skilled in the art that the present invention is not limited to the preferred embodiments and methods of use. On the contrary, the invention has a broader scope, which is defined by the scope of the claims. Other features and advantages of the invention will be apparent from the following description of the drawings. [Embodiment] In the following detailed description, the load 19 may include a Thermal Electrical Cooler (abbreviated as TEC). Depending on the direction of the current – the unit can operate in both heating and cooling modes. TECs are commonly used as heating/cooling elements to control the exact temperature of a device, especially in optical communication equipment. When forward current flows through the TEC, the TEC heats the device according to the exact temperature requirements; when the reverse current flows, the TEC will cool. In any event, the invention does not limit the use of such TEC loads or other loads. . The details of the description describe the main set of conditions in the transmission circuit power of the bidirectional load drive, etc., and will not discuss related conventional circuit characteristics and their applications such as overheat protection and overcurrent protection circuits' but these circuits can be included and considered Within the spirit and scope of the present invention. The present invention provides a differential load drive circuit (e.g., a bridge circuit) that operates in a linear mode and a PWM mode. The linear mode operation is used to reduce the current ripple of the differential load boat circuit operating at low currents. The switching points for linear mode and PWN mode are programmable or user defined. For example, it is possible to correlate the desired/allowable current through the load chopping, & bridge circuit

〇'\9!\9\〇37 D0C 1311402 Off-circuit pre-drive capability and/or other considerations to select the switching between the two modes of operation. The differential load drive circuit of the present invention functions as a load hunger (five) function in linear mode. With pwm mode. Therefore, the "low" of the low current flowing through the load mentioned herein can be interpreted broadly and can include any current value. The high current "high" mentioned in this article is only relative to low current (higher than low current) and should be interpreted as any current greater than the predefined low current through the load. In addition, the following detailed description of the embodiments will focus on various embodiments of the bridge differential load drive circuit. The operation of the H-bridge is well known in the art and will not be discussed here. I. First Embodiment Figs. 5 to 8 are a differential load driving circuit 50 according to a first exemplary embodiment of the present invention. In this illustrative embodiment, switch drive circuits 52, 54, 56, and 58 (corresponding to switches pi, p2, m, 分别, respectively) control the operation of the power mosfet switch. Current sources 60 and 62 are connected across the H_bridge to provide a linear current for the load. Each switch drive circuit 52, 54, 56 and 58 includes a plurality of switches (as shown) that selectively connect the power MOSFET switch to a PWM signal or power supply VCC, a PWM signal, a power supply VCC or ground. Switches 64 and 66 are used to provide a path for current source 60 or 62 to the respective load. In this illustrative embodiment, the switch drive circuit includes three switches that respectively connect the power MOSFET switch to the PWM signal, VCC and/or ground. These switches are shown in the switch drive circuits 52, 54, 56 and 58 and only one of the switches 52 and 5 can be connected to γ c C: at the same time. p type

O:\91\9I037 D0C 1311402 MOSFET switches p 1 and P2 are connected to vcc in linear mode. In the case of heating and cooling, N-type MOSFET switches (N1 and N2) are alternately connected to V C C and ground, respectively. Fig. 5 is an exemplary circuit diagram of an H_bridge load driving circuit 50 operating in a linear cooling mode in the first embodiment of the present invention. In this embodiment, the current source 6 〇 and the load are turned on by the switch 64 when the load 19 requires a low current. Current source 60 is typically a linear current source and may include pM〇s or nm〇s elements whose output current is controlled by an input voltage or current feedback signal (not shown, but such feedback control is Know to be familiar to the skilled person). At this time, the power switches PI, P2, and N2 are in a non-operating state via the MOSFET elements of the switches 52, 54 and 58, and there is no other switching operation, so the present invention eliminates the chopping of the load current. Of course, the current source can drive the load current. Figure 7 depicts the circuit 5〇' current source 62 operating in linear heating mode coupled to load 19 via switch 66. However, the current source cannot output a very large load current, and power consumption and efficiency may be an issue. If a large load current is required, the invention switches to the PWM mode of operation, as shown in Figure 6 (cooling) and Figure 8 (heating). When switching from the linear mode of operation to the PWM mode of operation or vice versa, the magnitude of the output current of linear current sources 60 and 62 needs to match the resultant current on the load driven by the initial PWM mode. This reduces the current discontinuity between the PWM mode of operation and the linear mode of operation (which is of course not necessary). This requirement helps to avoid potential oscillation problems with the current source or the entire feedback system. Curve 90 in Figure 9 depicts the region I of the linear mode and the region PWM of the PWM mode. Switching point 68 has been marked. As shown, this

〇 \9l\9l〇37 DOC 1311402 may need (but not necessarily) the starting current of the PWM mode switching point. Deliberately slightly less than the current of the linear mode switching point to ensure that the current control amount can cover all load currents. The current control amount can be the voltage of the load or the current feedback signal. II. The second embodiment If only a small heating current is needed in the application, Figure 5 and Figure 8 in the embodiment can be modified to 'remove or set the LC to reduce the number of reactive components, as shown in Figure 10, circuit 1 Shown. Figure 2 is an illustration of the operation of the second embodiment of the present invention. An exemplary circuit is driven by the H-bridge load in the PWM heating mode. Circuit 1 工作 operates in a lower linear heating current mode similar to that described above with respect to Figures 5 - 8 'including (via switch 丨〇 8) connecting current source 1 〇 6 to load 丨 9. In this embodiment, switch drive circuits 102 and 1 are similar to switch drive circuits 52 and 56 of Figures 5-8. The switch P2 includes a switch drive circuit 11A. In this case, the current source can be the external power PMOS P2 biased by the output of 〇TA (Output Transducer Amplifier). In accordance with these principles, similar circuits can be constructed for lower cooling current applications. The switch drive circuit 110 functions as a bias circuit for the PMOS device P2, which may include an operational amplifier 丨12 and a current or voltage feedback signal 114, which may be generated by comparing a feedback signal of the differential amplifier with a reference voltage. A bias voltage signal controls the conduction state of P2, so that P2 is equivalent to a current source. Of course, it will be understood by those skilled in the art that a variety of current sources are constructed which are considered equivalents of the present invention. III. Third Embodiment In the embodiment shown in Figs. 11 - 14, an Lc filter is removed. With before

0 \9I\9I037 DOC 1311402

The embodiment described differs in that this embodiment can output a higher heating or cooling current. Figure 11 is an exemplary circuit in which the H_bridge load driving circuit 200 of the third embodiment of the present invention operates in a linear cooling mode. Two current sources 2 1 0 and 2 12 are used in this embodiment. The current source 2 10 0 is a power source, and the current source 2 12 is operating with a sink current. When operating in the linear cooling mode, as shown in Figure 11, current source 21 〇 (via switch 2 14) is connected to the load 'N2' is fully ON (ON) and P2 is completely off (〇FF). P1 and N1 are in a disable state. Switching circuits 202, 204, 206 and 208 connect the power MOSFET to a suitable power source (e.g., p WM signal, VCC or ground) as shown in Figures 11-14. When operating in a linear heating mode ' as shown in Figure 13, current source 212 is connected to load 'P2 fully conductive (〇N), N2 is completely turned off (〇FF), and pw〇N1 is disabled. Figures 12 and 14 show the circuit 200 operating in the pwM cooling and heating mode, respectively. At this time, current sources 21A and 212 are disconnected from load 19, and 卩丨 and m are driven by the PWM signal (through switch drive circuits 2〇2 and 2〇4). P2*N2 alternates between V C C and ground. Of course, the skilled artisan knows that Figure 5 shows a controller that can be used to control the conduction state of the switch drive circuit and the switch of the current source. The output of controller 300 can include complementary PWM signals, PWMP and PWMN' for driving the PMOS and NMOS components of the differential load drive circuit, respectively. The 3H controller 300 also outputs switch control signals 302-308 to control the switching operation of the switch drive circuit (52, 54, 56, 58 in FIGS. 5-8); the controller 3 also generates the switch control signal 3 1 2 and 3 14 with control and current source

O:\9l\9l037 DOC 1311402 Connected switch (as shown in Figure 5-8) with current source 62 (four) switches 64 and 66) °, the controller: can know the use of conventional electric and / or current feedback signal The power delivered to the load in control, PWM mode, and linear mode. Some embodiments described in <, ^' may not require the controller to generate all of the signals, and as such, the controller may be modified to produce some suitable numbers. The controller fan can include a low current detector circuit... to control the switching point between the linear current mode and the PWM current mode. This detector circuit can further include a user-definable input threshold ^shoU) which sets the threshold current between the low current and pwM modes. Of course, the detector circuit 310 can be omitted by a predetermined input that is input into the controller, wherein the predetermined input represents the switching supply current (which can be defined by two). The controller can be constructed from a custom and/or off-the-shelf component. Such PWM controllers are well known in the art. It will be apparent to those skilled in the art that various modifications are possible herein. For example, the differential load driver circuit of the present invention employs a power m〇sfet tube, but other power switches known in the art, such as B-piece pick-ups and/or other switching devices, may be utilized. All such modifications and additions are considered to be within the scope of the invention. The scope of the invention is defined by the scope of the invention. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a conventional bridge load drive circuit operating in a cooling mode; Figure 2 is a conventional h_bridge load circuit operating in a heating mode;

O:\9I\91037 DOC 14 1311402

FIG. 3 is another conventional bridge driving circuit operating in a cooling mode; FIG. 4 is another conventional bridge driving circuit operating in a heating mode; FIG. 5 is in accordance with the present invention. An exemplary circuit diagram of a bridge load drive circuit operating in a linear cooling mode of the first embodiment; FIG. 6 is another illustration of an H-bridge load drive circuit operating in a pwM cooling mode in accordance with a first embodiment of the present invention. FIG. 7 is another exemplary circuit diagram of an H-bridge load driving circuit operating in a linear heating mode according to a first embodiment of the present invention; FIG. 8 is a working mode in a pwM heating mode according to a first embodiment of the present invention. Another exemplary circuit diagram of the lower H-bridge load driving circuit; FIG. 9 is a diagram showing the relationship between the linear current mode and the pWM mode; FIG. 1 is a PWM heating mode according to the second embodiment of the present invention. FIG. 11 is an exemplary circuit diagram of an H-bridge load driving circuit operating in a linear cooling mode according to a third embodiment of the present invention; FIG. Another exemplary circuit diagram of an H-bridge load driving circuit operating in a PWM cooling mode according to a third embodiment of the present invention; FIG. 13 is an H-bridge operating in a linear heating mode according to a third embodiment of the present invention. Another exemplary circuit diagram of a load driving circuit; FIG. 14 is another exemplary circuit diagram of an H-bridge load driving circuit operating in a pwM heating mode in accordance with a third embodiment of the present invention;

〇 \9I\9I037 DOC -15- 1311402 Figure 15 is an exemplary controller for controlling the operation of a load drive circuit in accordance with the present invention. [Description of Symbols] 10, 20 H-bridge circuit 12, 14, 16, 18 Switch 19 Load 50 Differential load horse circuit 52, 54, 56 '58 Switch drive circuit 60 ' 62 Current source 64 ' 66 Switch 68 switching point 90 curve 100 circuit 102 > 104 > 108, 110 switch drive circuit 106 current source 112 operational amplifier 114 current or voltage feedback signal 200 H - bridge load drive circuit 202 ' 204 ' 206, 208 switch circuit 210 , 212 Current Source 214, 216 Switch 300 Controller 302, 304, 306, 308 '312' 314 Switch Control Signal 310 Low Current Detector Circuit O\9l\9l037.DOC -16-

Claims (1)

1311402 ROC (Taiwan) Patent Application No. 093102508 Replacement Version of Chinese Claims (November 2008) Bamboo (l 1. A differential load drive circuit comprising: a plurality of power switches coupled to a load and powering the load, wherein each The power-on relationship is fully turned on (fu 11 y ο η) or fully turned off (fu 11 y off); a plurality of power switch driving circuits, the plurality of power switch driving circuits respectively controlling switching states of the plurality of power switches, And selectively coupling at least one to a pulse width modulation (PWM) signal of the plurality of power switches to enable a pulse width modulation power supply mode, the plurality of power switch driving circuits including a first switch driving circuit, The method includes: a first switch coupled to and decoupled from the first current source and the load; and a second switch coupled in parallel with the first switch, coupled and decoupled Connecting a first power switch and a voltage source; a third switch coupled in parallel with the second switch, and coupling and decoupling the first power switch and the pulse width a fourth switch, coupled in parallel with the first switch, coupled and decoupled to a second power switch and a ground; and a fifth switch coupled to the fourth switch Parallelly coupling, coupling and decoupling the second power switch and the pulse width modulation signal; and a controller for controlling the plurality of power switch driving circuits, and for selecting the pulse width modulation signal Controlling the pulse 131122 width modulation power supply mode of the at least one power switch, or selecting the first current source to provide a current to one of the load linear power supply modes, and controlling the pulse width adjustment according to a preset threshold value a switchover point between the variable power supply mode and the linear power supply mode to achieve a specified chopping current of the load. 2. The differential load drive circuit of claim 1 wherein the pulse width The modulated power supply mode includes a cooling mode and a heating mode, wherein a current direction flowing through the load in the cooling mode flows through the load in the heating mode 3. The current direction is opposite. 3. The differential load driving circuit of claim 1, wherein the linear power supply mode includes a cooling mode and a heating mode, wherein a current direction flowing through the load in the cooling mode is The current flowing through the load is reversed in the heating mode. 4. The differential load driving circuit of claim 3, further comprising a second current source, wherein the first current source supplies the load in the cooling mode And wherein the second current source supplies power to the load in the heating mode. 5. The differential load driving circuit of claim 1, further comprising at least one filter circuit interposed between at least two of the plurality of power switches and the load. 6. The differential load drive circuit of claim 1, wherein the load comprises a Thermal Electrical Cooler. 1311402 7. The differential load driving circuit of claim 1, wherein in the pulse width modulation power supply mode, one of the switching points has a load current slightly smaller than a load current of the switching point in the linear power supply mode. . 8. The differential load drive circuit of claim 1, wherein the specified chop current is higher than zero. 9. The differential load drive circuit of claim 1, wherein the controller includes an input to receive the predetermined threshold. 10. The differential load driving circuit of claim 1, wherein the controller further receives a feedback signal from the load in the linear power supply mode and the pulse width modulation power supply mode to control transmission to the load The power. 11. The differential load drive circuit of claim 1, wherein the first current source is decoupled from the load in the pulse width modulation supply mode. 12. An H-bridge load drive circuit, the circuit comprising: four power switches forming an H-bridge circuit, the four power switches being coupled to a load to selectively supply current to the load, wherein the four Each of the power switches is fully ful on or fully off; a plurality of power switch drive circuits are operative to control the switching states of the four power switches and selectively couple the same At least two to one pulse width modulation (PWM) signal of the four power switches to enable a pulse width modulation of the 1311402 variable power supply mode; at least one current source is selectively coupled to the load and used to supply the load a current to enable a linear power supply mode; at least one current source switch operative to couple the at least one current source to the load; and a controller to control the plurality of power switch drive circuits and the at least one current source switch And selecting the pulse width modulation signal to control the pulse width modulation power supply mode of the at least two power switches, or selecting the at least one current source to provide Flowing to the linear power supply mode of the load, and controlling a switching point between the pulse width modulation power supply mode and the linear power supply mode according to a preset threshold to achieve a specified chopping current of the load . 13. The H-bridge load driving circuit of claim 12, wherein the linear power supply mode comprises a cooling mode and a heating mode, wherein a current direction flowing through the load in the cooling mode is coupled to the heating The current flowing through the load in the mode is in the opposite direction. 14. The H-bridge load driving circuit of claim 12, wherein the pulse width modulation power supply mode comprises a cooling mode and a heating mode, wherein 'the current direction flowing through the load in the cooling core mode The direction of the current flowing through the load in this heating mode is opposite. 15. The H-bridge load driving circuit of claim 12, wherein the 1311402 controller receives and returns a signal from the load in the linear power supply mode and the pulse width modulation power supply mode to Controls the electrical energy delivered to the load. 16· Shen. The η-bridge load drive circuit of the 12th patent range, wherein the at least-current source is decoupled from the load in the pulse width modulation supply mode. 17. A differential load drive circuit, the circuit comprising: a plurality of power switches connected to a load and selectively powering a load under control of a plurality of power switch drive circuits, wherein each of the plurality of power switches Is either fully conductive (fulIy〇n) or fully closed (fuUy〇ff); - the first current source' selectively engages the load to supply current to the load to enable a linear supply of lightning a deep power supply mode, wherein the plurality of power switch driving circuits comprise a first switch driving circuit, comprising: a first switch 'connecting and decoupling the first current source and the load; a second switch is connected in parallel with the first switch, and is lightly connected and decoupled to a first power switch and a voltage source; a third switch is connected in parallel with the second switch The first power switch and the pulse width modulation (TO) signal are connected to the first power switch, and the fourth switch is connected to the first switch in a lightly connected manner, and is lightly connected and decoupled to a second power switch and - ground terminal; and 1311242 a fifth switch The second switch is coupled in parallel with the fourth switch, and coupled to the second power switch and the pulse width modulation signal; and a controller for controlling the first, second, third, a fourth and fifth switch and the first current source, and configured to select the pulse width modulation signal to control a pulse width modulation power supply mode of the at least one of the plurality of power switches, or select the first current source to provide a linear current supply mode to the load, and configured to control a switchover point between the pulse width modulation power supply mode and the linear power supply mode according to a predetermined threshold to achieve the load A specified chopping current. 18. The differential load drive circuit of claim 17 wherein the linear power supply mode includes a low current mode in which the direction of current flow through the load is defined as a cooling mode. 19. The differential load drive circuit of claim 17 wherein the linear power supply mode comprises a low current mode in which the direction of current flow through the load is defined as a heating mode. 20. The differential load drive circuit of claim 17 wherein the pulse width modulation supply mode comprises a current mode in which the direction of current flow through the load is defined as a cooling mode. 21. The differential load drive circuit of claim 17 wherein the pulse width modulated power supply mode comprises a south current mode in which the direction of current flow through the load is defined as a heating mode. 1311402 22. If the application of the scope of the patent item 17 贞 _ _ circuit, the step-by-step includes a switch state of the power switch driver and is used to select the wide control of the plurality of power sources at least 'to enable Pulse width modulation power supply to the pulse width modulation signal for selectively switching the plurality of power switch modes 23. The differential load drive circuit of claim 17 further includes: at least - a current source switch for The first current source is switched to the load to enable the linear power supply mode. 24. The differential load driving circuit of claim 17, wherein the controller further receives a feedback signal from the load in the linear power supply mode and the pulse width modulation power supply mode to control transmission to the load The power. 25. The differential load driving circuit of claim 17, wherein the first current source is connected to the load in the pulse width modulation power supply mode.